adjust error codes in merchant

37 files changed, 627 insertions, 467 deletions

diff --git a/src/backend/taler-merchant-httpd.c b/src/backend/taler-merchant-httpd.c
index 0ae3b4ce..1dcc51c8 100644
--- a/src/backend/taler-merchant-httpd.c
+++ b/src/backend/taler-merchant-httpd.c
@@ -1547,12 +1547,12 @@ url_handler (void *cls,
            (url_found) )
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_METHOD_NOT_ALLOWED,
-                                           TALER_EC_METHOD_INVALID,
+                                           TALER_EC_GENERIC_METHOD_INVALID,
                                            method);
       if (NULL == hc->rh)
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_NOT_FOUND,
-                                           TALER_EC_ENDPOINT_UNKNOWN,
+                                           TALER_EC_GENERIC_ENDPOINT_UNKNOWN,
                                            hc->url);
     }
   }
@@ -1562,7 +1562,7 @@ url_handler (void *cls,
        (GNUNET_YES != hc->rh->skip_instance) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_INSTANCE_UNKNOWN,
+                                       TALER_EC_MERCHANT_GENERIC_INSTANCE_UNKNOWN,
                                        url);
   hc->has_body = ( (0 == strcasecmp (method,
                                      MHD_HTTP_METHOD_POST)) ||
@@ -1597,7 +1597,7 @@ url_handler (void *cls,
         GNUNET_break_op (0);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_PAYLOAD_TOO_LARGE,
-                                           TALER_EC_UPLOAD_EXCEEDS_LIMIT,
+                                           TALER_EC_GENERIC_UPLOAD_EXCEEDS_LIMIT,
                                            cl);
       }
     }
diff --git a/src/backend/taler-merchant-httpd_auditors.c b/src/backend/taler-merchant-httpd_auditors.c
index c7e7e584..179fa320 100644
--- a/src/backend/taler-merchant-httpd_auditors.c
+++ b/src/backend/taler-merchant-httpd_auditors.c
@@ -76,7 +76,7 @@ TMH_AUDITORS_check_dk (struct TALER_EXCHANGE_Handle *mh,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Denomination key offered by client has expired for deposits\n");
     *hc = MHD_HTTP_GONE;
-    *ec = TALER_EC_PAY_DENOMINATION_DEPOSIT_EXPIRED;
+    *ec = TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_DENOMINATION_DEPOSIT_EXPIRED;
     return GNUNET_SYSERR; /* expired */
   }
   if (exchange_trusted)
@@ -90,8 +90,9 @@ TMH_AUDITORS_check_dk (struct TALER_EXCHANGE_Handle *mh,
   {
     /* this should never happen, keys should have been successfully
        obtained before we even got into this function */
-    *ec = TALER_EC_PAY_EXCHANGE_HAS_NO_KEYS;
-    *hc = MHD_HTTP_FAILED_DEPENDENCY;
+    GNUNET_break (0);
+    *ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+    *hc = MHD_HTTP_INTERNAL_SERVER_ERROR;
     return GNUNET_SYSERR;
   }
   for (unsigned int i = 0; i<keys->num_auditors; i++)
@@ -120,7 +121,7 @@ TMH_AUDITORS_check_dk (struct TALER_EXCHANGE_Handle *mh,
               "Denomination key %s offered by client not audited by any accepted auditor\n",
               GNUNET_h2s (&dk->h_key));
   *hc = MHD_HTTP_BAD_REQUEST;
-  *ec = TALER_EC_PAY_DENOMINATION_KEY_AUDITOR_FAILURE;
+  *ec = TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_DENOMINATION_KEY_AUDITOR_FAILURE;
   return GNUNET_NO;
 }
 
diff --git a/src/backend/taler-merchant-httpd_exchanges.c b/src/backend/taler-merchant-httpd_exchanges.c
index e882f557..2c8995ee 100644
--- a/src/backend/taler-merchant-httpd_exchanges.c
+++ b/src/backend/taler-merchant-httpd_exchanges.c
@@ -372,7 +372,7 @@ process_wire_fees (struct Exchange *exchange,
   {
     /* Hole in the fee structure, not allowed! */
     GNUNET_break_op (0);
-    return TALER_EC_HOLE_IN_WIRE_FEE_STRUCTURE;
+    return TALER_EC_MERCHANT_GENERIC_HOLE_IN_WIRE_FEE_STRUCTURE;
   }
   while (NULL != fees)
   {
@@ -477,7 +477,7 @@ process_wire_accounts (struct Exchange *exchange,
     {
       /* malformed payto:// URI returned by exchange */
       GNUNET_break_op (0);
-      return TALER_EC_PAYTO_MALFORMED;
+      return TALER_EC_GENERIC_PAYTO_URI_MALFORMED;
     }
     ec = process_wire_fees (exchange,
                             master_pub,
diff --git a/src/backend/taler-merchant-httpd_get-orders-ID.c b/src/backend/taler-merchant-httpd_get-orders-ID.c
index 5c6949bb..c0922f67 100644
--- a/src/backend/taler-merchant-httpd_get-orders-ID.c
+++ b/src/backend/taler-merchant-httpd_get-orders-ID.c
@@ -694,7 +694,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
         GNUNET_break_op (0);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "token");
       }
     }
@@ -714,7 +714,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
         GNUNET_break_op (0);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "h_contract");
       }
     }
@@ -738,7 +738,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
           GNUNET_break_op (0);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_PARAMETER_MALFORMED,
+                                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                              "timeout_ms (must be non-negative number)");
         }
         god->sc.long_poll_timeout
@@ -783,7 +783,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
           GNUNET_break_op (0);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_PARAMETER_MALFORMED,
+                                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                              "refund");
         }
         god->sc.awaiting_refund = true;
@@ -815,8 +815,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "contract terms");
     }
   }
 
@@ -834,8 +834,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_free (god);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_INTERNAL_LOGIC_ERROR,
-                                         "could not hash contract terms");
+                                         TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
+                                         "contract terms");
     }
     contract_match = (0 ==
                       GNUNET_memcmp (&h,
@@ -845,10 +845,11 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
          (! contract_match) )
     {
       GNUNET_break_op (0);
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_FORBIDDEN,
-                                         TALER_EC_GET_ORDER_WRONG_CONTRACT,
-                                         NULL);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_FORBIDDEN,
+        TALER_EC_MERCHANT_GENERIC_CONTRACT_HASH_DOES_NOT_MATCH_ORDER,
+        NULL);
     }
   }
 
@@ -874,8 +875,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "order");
     }
     god->unclaimed = (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs) &&
                      ! contract_available;
@@ -887,7 +888,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
                   order_id);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_GET_ORDERS_ID_UNKNOWN,
+                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                          order_id);
     }
     token_match = (0 == GNUNET_memcmp (&db_claim_token,
@@ -901,7 +902,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_ORDERS_CONTRACT_CONTENT_INVALID,
+                                       TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
                                        order_id);
   }
 
@@ -921,7 +922,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_FORBIDDEN,
-                                       TALER_EC_MERCHANT_GET_ORDER_INVALID_TOKEN,
+                                       TALER_EC_MERCHANT_GET_ORDERS_ID_INVALID_TOKEN,
                                        NULL);
   }
   if ( ( (! token_match) ||
@@ -932,13 +933,14 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
     {
       if (GNUNET_NO ==
           GNUNET_is_zero (&god->h_contract_terms))
-        return TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_FORBIDDEN,
-                                           TALER_EC_GET_ORDER_WRONG_CONTRACT,
-                                           NULL);
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_FORBIDDEN,
+          TALER_EC_MERCHANT_GENERIC_CONTRACT_HASH_DOES_NOT_MATCH_ORDER,
+          NULL);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_FORBIDDEN,
-                                         TALER_EC_MERCHANT_GET_ORDER_INVALID_TOKEN,
+                                         TALER_EC_MERCHANT_GET_ORDERS_ID_INVALID_TOKEN,
                                          NULL);
     }
     if (god->generate_html)
@@ -1014,8 +1016,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "order by fulfillment");
     }
     if ( (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs) ||
          (0 != strcmp (order_id,
@@ -1052,8 +1054,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "order status");
     }
     GNUNET_break (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs);
     GNUNET_break (0 ==
@@ -1084,8 +1086,8 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "refunds, detailed");
   }
 
   if ( ((god->sc.awaiting_refund) &&
@@ -1134,7 +1136,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
           GNUNET_break (0);
           return TALER_MHD_reply_with_error (god->sc.con,
                                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_ALLOCATION_FAILURE,
+                                             TALER_EC_GENERIC_ALLOCATION_FAILURE,
                                              "refund URI");
         }
         qr = TMH_create_qrcode (uri);
@@ -1144,7 +1146,7 @@ TMH_get_orders_ID (const struct TMH_RequestHandler *rh,
           GNUNET_free (uri);
           return TALER_MHD_reply_with_error (god->sc.con,
                                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_ALLOCATION_FAILURE,
+                                             TALER_EC_GENERIC_ALLOCATION_FAILURE,
                                              "qr code");
         }
         {
diff --git a/src/backend/taler-merchant-httpd_get-tips-ID.c b/src/backend/taler-merchant-httpd_get-tips-ID.c
index 5fa257fc..fd60c6e9 100644
--- a/src/backend/taler-merchant-httpd_get-tips-ID.c
+++ b/src/backend/taler-merchant-httpd_get-tips-ID.c
@@ -171,7 +171,7 @@ TMH_get_tips_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        hc->infix);
   }
 
@@ -193,7 +193,7 @@ TMH_get_tips_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_TIPS_DB_LOOKUP_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                                        NULL);
   }
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
@@ -203,7 +203,7 @@ TMH_get_tips_ID (const struct TMH_RequestHandler *rh,
                 hc->infix);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_GET_TIPS_ID_UNKNOWN,
+                                       TALER_EC_MERCHANT_GENERIC_TIP_ID_UNKNOWN,
                                        hc->infix);
   }
 
@@ -238,7 +238,7 @@ TMH_get_tips_ID (const struct TMH_RequestHandler *rh,
         GNUNET_free (uri);
         ret = TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                          TALER_EC_ALLOCATION_FAILURE,
+                                          TALER_EC_GENERIC_ALLOCATION_FAILURE,
                                           "during QR code generation");
       }
       else
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-abort.c b/src/backend/taler-merchant-httpd_post-orders-ID-abort.c
index cfb5bb72..4f6b8667 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-abort.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-abort.c
@@ -32,8 +32,9 @@
 /**
  * How long to wait before giving up processing with the exchange?
  */
-#define ABORT_TIMEOUT (GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, \
-                                                      30))
+#define ABORT_GENERIC_TIMEOUT (GNUNET_TIME_relative_multiply ( \
+                                 GNUNET_TIME_UNIT_SECONDS, \
+                                 30))
 
 /**
  * How often do we retry the (complex!) database transaction?
@@ -349,7 +350,7 @@ generate_success_response (struct AbortContext *ac)
     GNUNET_break (0);
     resume_abort_with_error (ac,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_JSON_ALLOCATION_FAILURE,
+                             TALER_EC_GENERIC_JSON_ALLOCATION_FAILURE,
                              "could not create JSON array");
     return;
   }
@@ -386,7 +387,7 @@ generate_success_response (struct AbortContext *ac)
       GNUNET_break (0);
       resume_abort_with_error (ac,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_JSON_ALLOCATION_FAILURE,
+                               TALER_EC_GENERIC_JSON_ALLOCATION_FAILURE,
                                "could not create JSON array");
       return;
     }
@@ -518,27 +519,35 @@ process_abort_with_exchange (void *cls,
   (void) exchange_trusted;
   ac->fo = NULL;
   GNUNET_assert (GNUNET_YES == ac->suspended);
-  if (MHD_HTTP_OK != hr->http_status)
+  if (NULL == hr)
   {
-    /* The request failed somehow */
-    GNUNET_break_op (0);
     resume_abort_with_response (
       ac,
-      MHD_HTTP_FAILED_DEPENDENCY,
+      MHD_HTTP_GATEWAY_TIMEOUT,
       TALER_MHD_make_json_pack (
-        (NULL != hr->reply)
-        ? "{s:s, s:I, s:I, s:I, s:O}"
-        : "{s:s, s:I, s:I, s:I}",
+        "{s:s, s:I}",
         "hint",
-        TALER_ErrorCode_get_hint (TALER_EC_ABORT_EXCHANGE_KEYS_FAILURE),
+        TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT),
         "code",
-        (json_int_t) TALER_EC_ABORT_EXCHANGE_KEYS_FAILURE,
-        "exchange_http_status",
-        (json_int_t) hr->http_status,
-        "exchange_code",
-        (json_int_t) hr->ec,
-        "exchange_reply",
-        hr->reply));
+        (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT));
+    return;
+  }
+  if (NULL == exchange_handle)
+  {
+    /* The request failed somehow */
+    GNUNET_break_op (0);
+    resume_abort_with_response (
+      ac,
+      MHD_HTTP_BAD_GATEWAY,
+      TALER_MHD_make_json_pack (
+        "{s:s, s:I, s:I, s:I, s:O?}",
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE),
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE,
+        "exchange_http_status", (json_int_t) hr->http_status,
+        "exchange_code", (json_int_t) hr->ec,
+        "exchange_reply", hr->reply));
     return;
   }
   /* Initiate refund operation for all coins of
@@ -569,7 +578,7 @@ process_abort_with_exchange (void *cls,
       GNUNET_break_op (0);
       resume_abort_with_error (ac,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_ABORT_EXCHANGE_REFUND_FAILED,
+                               TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_EXCHANGE_REFUND_FAILED,
                                "Failed to start refund with exchange");
       return;
     }
@@ -615,7 +624,7 @@ find_next_exchange (struct AbortContext *ac)
         GNUNET_break (0);
         resume_abort_with_error (ac,
                                  MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                 TALER_EC_ABORT_EXCHANGE_LOOKUP_FAILED,
+                                 TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_EXCHANGE_LOOKUP_FAILED,
                                  "Failed to lookup exchange by URL");
         return;
       }
@@ -691,8 +700,8 @@ refund_coins (void *cls,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       resume_abort_with_error (ac,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_ABORT_DB_STORE_ABORT_ERROR,
-                               "Merchant database error storing abort-refund");
+                               TALER_EC_GENERIC_DB_STORE_FAILED,
+                               "refund_coin");
       return;
     }
   } /* for all coins */
@@ -716,8 +725,8 @@ begin_transaction (struct AbortContext *ac)
     GNUNET_break (0);
     resume_abort_with_error (ac,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_ABORT_DB_STORE_TRANSACTION_ERROR,
-                             "Soft merchant database error: retry counter exceeded");
+                             TALER_EC_GENERIC_DB_SOFT_FAILURE,
+                             NULL);
     return;
   }
   GNUNET_assert (GNUNET_YES == ac->suspended);
@@ -731,8 +740,8 @@ begin_transaction (struct AbortContext *ac)
     GNUNET_break (0);
     resume_abort_with_error (ac,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_ABORT_DB_FETCH_TRANSACTION_ERROR,
-                             "Merchant database error (could not begin transaction)");
+                             TALER_EC_GENERIC_DB_START_FAILED,
+                             NULL);
     return;
   }
 
@@ -763,14 +772,14 @@ begin_transaction (struct AbortContext *ac)
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       resume_abort_with_error (ac,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_ABORT_DB_FETCH_TRANSACTION_ERROR,
-                               "Merchant database error");
+                               TALER_EC_GENERIC_DB_FETCH_FAILED,
+                               "order status");
       return;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       TMH_db->rollback (TMH_db->cls);
       resume_abort_with_error (ac,
                                MHD_HTTP_NOT_FOUND,
-                               TALER_EC_ABORT_CONTRACT_NOT_FOUND,
+                               TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_CONTRACT_NOT_FOUND,
                                "Could not find contract");
       return;
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
@@ -780,7 +789,7 @@ begin_transaction (struct AbortContext *ac)
         TMH_db->rollback (TMH_db->cls);
         resume_abort_with_error (ac,
                                  MHD_HTTP_PRECONDITION_FAILED,
-                                 TALER_EC_ABORT_REFUND_REFUSED_PAYMENT_COMPLETE,
+                                 TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_REFUND_REFUSED_PAYMENT_COMPLETE,
                                  "Payment was complete, refusing to abort");
         return;
       }
@@ -792,7 +801,7 @@ begin_transaction (struct AbortContext *ac)
       GNUNET_break_op (0);
       resume_abort_with_error (ac,
                                MHD_HTTP_FORBIDDEN,
-                               TALER_EC_ABORT_CONTRACT_HASH_MISSMATCH,
+                               TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_CONTRACT_HASH_MISSMATCH,
                                "Provided hash does not match order on file");
       return;
     }
@@ -816,8 +825,8 @@ begin_transaction (struct AbortContext *ac)
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     resume_abort_with_error (ac,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_ABORT_DB_FETCH_TRANSACTION_ERROR,
-                             "Merchant database error");
+                             TALER_EC_GENERIC_DB_FETCH_FAILED,
+                             "deposits");
     return;
   }
 
@@ -832,8 +841,8 @@ begin_transaction (struct AbortContext *ac)
     }
     resume_abort_with_error (ac,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_ABORT_DB_STORE_ABORT_ERROR,
-                             "Merchant database error: could not commit");
+                             TALER_EC_GENERIC_DB_COMMIT_FAILED,
+                             NULL);
     return;
   }
 
@@ -889,7 +898,7 @@ parse_abort (struct MHD_Connection *connection,
     GNUNET_JSON_parse_free (spec);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_ABORT_COINS_ARRAY_EMPTY,
+                                       TALER_EC_MERCHANT_POST_ORDERS_ID_ABORT_COINS_ARRAY_EMPTY,
                                        "coins");
   }
   /* note: 1 coin = 1 deposit confirmation expected */
@@ -957,9 +966,9 @@ handle_abort_timeout (void *cls)
     ac->fo = NULL;
   }
   resume_abort_with_error (ac,
-                           MHD_HTTP_REQUEST_TIMEOUT,
-                           TALER_EC_ABORT_EXCHANGE_TIMEOUT,
-                           "likely the exchange did not reply quickly enough");
+                           MHD_HTTP_GATEWAY_TIMEOUT,
+                           TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT,
+                           NULL);
 }
 
 
@@ -1023,7 +1032,7 @@ TMH_post_orders_ID_abort (const struct TMH_RequestHandler *rh,
   ac->suspended = GNUNET_YES;
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Suspending abort handling while working with the exchange\n");
-  ac->timeout_task = GNUNET_SCHEDULER_add_delayed (ABORT_TIMEOUT,
+  ac->timeout_task = GNUNET_SCHEDULER_add_delayed (ABORT_GENERIC_TIMEOUT,
                                                    &handle_abort_timeout,
                                                    ac);
   begin_transaction (ac);
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-claim.c b/src/backend/taler-merchant-httpd_post-orders-ID-claim.c
index 5580fb20..f82ed061 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-claim.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-claim.c
@@ -201,24 +201,24 @@ TMH_post_orders_ID_claim (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_ORDERS_CLAIM_HARD_DB_ERROR,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_ORDERS_CLAIM_SOFT_DB_ERROR,
+                                       TALER_EC_GENERIC_DB_SOFT_FAILURE,
                                        NULL);
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     if (NULL == contract_terms)
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_ORDERS_CLAIM_NOT_FOUND,
+                                         TALER_EC_MERCHANT_POST_ORDERS_ID_CLAIM_NOT_FOUND,
                                          order_id);
     /* already claimed! */
     json_decref (contract_terms);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_CONFLICT,
-                                       TALER_EC_ORDERS_ALREADY_CLAIMED,
+                                       TALER_EC_MERCHANT_POST_ORDERS_ID_CLAIM_ALREADY_CLAIMED,
                                        order_id);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     GNUNET_assert (NULL != contract_terms);
@@ -240,7 +240,7 @@ TMH_post_orders_ID_claim (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_INTERNAL_LOGIC_ERROR,
+                                         TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                          NULL);
     }
 
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-paid.c b/src/backend/taler-merchant-httpd_post-orders-ID-paid.c
index effc4e12..1e692bfc 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-paid.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-paid.c
@@ -77,7 +77,7 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_FORBIDDEN,
-                                       TALER_EC_PAID_COIN_SIGNATURE_INVALID,
+                                       TALER_EC_MERCHANT_POST_ORDERS_ID_PAID_COIN_SIGNATURE_INVALID,
                                        NULL);
   }
 
@@ -100,8 +100,8 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_PAID_DB_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "contract terms");
   }
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
   {
@@ -110,7 +110,7 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
                 order_id);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_PAID_ORDER_UNKNOWN,
+                                       TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                        order_id);
   }
 
@@ -125,8 +125,8 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
       json_decref (contract_terms);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_INTERNAL_LOGIC_ERROR,
-                                         "Could not hash contract terms");
+                                         TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
+                                         NULL);
     }
     if (0 != GNUNET_memcmp (&pr.h_contract_terms,
                             &h_contract_terms))
@@ -134,7 +134,7 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
       json_decref (contract_terms);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_CONFLICT,
-                                         TALER_EC_PAID_CONTRACT_HASH_MISMATCH,
+                                         TALER_EC_MERCHANT_POST_ORDERS_ID_PAID_CONTRACT_HASH_MISMATCH,
                                          NULL);
     }
   }
@@ -147,7 +147,7 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
       json_decref (contract_terms);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PAID_DB_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
                                          NULL);
     }
     {
@@ -179,8 +179,8 @@ TMH_post_orders_ID_paid (const struct TMH_RequestHandler *rh,
       json_decref (contract_terms);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PAID_DB_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_STORE_FAILED,
+                                         "mark contract paid");
     }
   }
   if (NULL != session_id)
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-pay.c b/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
index 0e033a7f..93835a24 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-pay.c
@@ -594,14 +594,15 @@ deposit_cb (void *cls,
     {
       /* internal server error at exchange */
       resume_pay_with_response (pc,
-                                MHD_HTTP_FAILED_DEPENDENCY,
+                                MHD_HTTP_BAD_GATEWAY,
                                 TALER_MHD_make_json_pack (
                                   "{s:s, s:I, s:I, s:I}",
                                   "hint",
                                   TALER_ErrorCode_get_hint (
-                                    TALER_EC_PAY_EXCHANGE_FAILED),
+                                    TALER_EC_MERCHANT_GENERIC_EXCHANGE_UNEXPECTED_STATUS),
                                   "code",
-                                  (json_int_t) TALER_EC_PAY_EXCHANGE_FAILED,
+                                  (json_int_t)
+                                  TALER_EC_MERCHANT_GENERIC_EXCHANGE_UNEXPECTED_STATUS,
                                   "exchange_code",
                                   (json_int_t) hr->ec,
                                   "exchange_http_status",
@@ -612,14 +613,14 @@ deposit_cb (void *cls,
       /* We can't do anything meaningful here, the exchange did something wrong */
       resume_pay_with_response (
         pc,
-        MHD_HTTP_FAILED_DEPENDENCY,
+        MHD_HTTP_BAD_GATEWAY,
         TALER_MHD_make_json_pack (
           "{s:s, s:I, s:I, s:I}",
           "hint",
           TALER_ErrorCode_get_hint (
-            TALER_EC_PAY_EXCHANGE_REPLY_MALFORMED),
+            TALER_EC_MERCHANT_GENERIC_EXCHANGE_REPLY_MALFORMED),
           "code",
-          (json_int_t) TALER_EC_PAY_EXCHANGE_REPLY_MALFORMED,
+          (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_REPLY_MALFORMED,
           "exchange_code",
           (json_int_t) hr->ec,
           "exchange_http_status",
@@ -629,16 +630,17 @@ deposit_cb (void *cls,
     {
       /* Forward error, adding the "coin_pub" for which the
          error was being generated */
-      if (TALER_EC_DEPOSIT_INSUFFICIENT_FUNDS == hr->ec)
+      if (TALER_EC_EXCHANGE_DEPOSIT_INSUFFICIENT_FUNDS == hr->ec)
         resume_pay_with_response (
           pc,
           MHD_HTTP_CONFLICT,
           TALER_MHD_make_json_pack ("{s:s, s:I, s:I, s:I, s:o, s:O}",
                                     "hint",
                                     TALER_ErrorCode_get_hint (
-                                      TALER_EC_PAY_INSUFFICIENT_FUNDS),
+                                      TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_INSUFFICIENT_FUNDS),
                                     "code",
-                                    (json_int_t) TALER_EC_PAY_INSUFFICIENT_FUNDS,
+                                    (json_int_t)
+                                    TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_INSUFFICIENT_FUNDS,
                                     "exchange_code",
                                     (json_int_t) hr->ec,
                                     "exchange_http_status",
@@ -650,13 +652,14 @@ deposit_cb (void *cls,
       else
         resume_pay_with_response (
           pc,
-          MHD_HTTP_FAILED_DEPENDENCY,
+          MHD_HTTP_BAD_GATEWAY,
           TALER_MHD_make_json_pack ("{s:s, s:I, s:I, s:I, s:o, s:O}",
                                     "hint",
                                     TALER_ErrorCode_get_hint (
-                                      TALER_EC_PAY_EXCHANGE_FAILED),
+                                      TALER_EC_MERCHANT_GENERIC_EXCHANGE_UNEXPECTED_STATUS),
                                     "code",
-                                    (json_int_t) TALER_EC_PAY_EXCHANGE_FAILED,
+                                    (json_int_t)
+                                    TALER_EC_MERCHANT_GENERIC_EXCHANGE_UNEXPECTED_STATUS,
                                     "exchange_code",
                                     (json_int_t) hr->ec,
                                     "exchange_http_status",
@@ -703,8 +706,8 @@ deposit_cb (void *cls,
     /* Forward error including 'proof' for the body */
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_STORE_PAY_ERROR,
-                           "Merchant database error");
+                           TALER_EC_GENERIC_DB_STORE_FAILED,
+                           "deposit");
     return;
   }
   dc->found_in_db = true; /* well, at least NOW it'd be true ;-) */
@@ -743,28 +746,34 @@ process_pay_with_exchange (void *cls,
   (void) payto_uri;
   pc->fo = NULL;
   GNUNET_assert (GNUNET_YES == pc->suspended);
-  if (MHD_HTTP_OK != hr->http_status)
+  if (NULL == hr)
   {
-    /* The request failed somehow */
-    GNUNET_break_op (0);
     resume_pay_with_response (
       pc,
-      MHD_HTTP_FAILED_DEPENDENCY,
+      MHD_HTTP_GATEWAY_TIMEOUT,
       TALER_MHD_make_json_pack (
-        (NULL != hr->reply)
-        ? "{s:s, s:I, s:I, s:I, s:O}"
-        : "{s:s, s:I, s:I, s:I}",
+        "{s:s, s:I}",
         "hint",
         TALER_ErrorCode_get_hint (
-          TALER_EC_PAY_EXCHANGE_KEYS_FAILURE),
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT),
         "code",
-        (json_int_t) TALER_EC_PAY_EXCHANGE_KEYS_FAILURE,
-        "exchange_http_status",
-        (json_int_t) hr->http_status,
-        "exchange_code",
-        (json_int_t) hr->ec,
-        "exchange_reply",
-        hr->reply));
+        (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT));
+    return;
+  }
+  if (NULL == exchange_handle)
+  {
+    GNUNET_break_op (0);
+    resume_pay_with_response (
+      pc,
+      MHD_HTTP_BAD_GATEWAY,
+      TALER_MHD_make_json_pack (
+        "{s:s, s:I, s:I, s:I, s:O?}",
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE),
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE,
+        "exchange_http_status", (json_int_t) hr->http_status,
+        "exchange_code", (json_int_t) hr->ec,
+        "exchange_reply", hr->reply));
     return;
   }
   keys = TALER_EXCHANGE_get_keys (exchange_handle);
@@ -772,9 +781,9 @@ process_pay_with_exchange (void *cls,
   {
     GNUNET_break (0); /* should not be possible if HTTP status is #MHD_HTTP_OK */
     resume_pay_with_error (pc,
-                           MHD_HTTP_FAILED_DEPENDENCY,
-                           TALER_EC_PAY_EXCHANGE_KEYS_FAILURE,
-                           "no keys");
+                           MHD_HTTP_BAD_GATEWAY,
+                           TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE,
+                           NULL);
     return;
   }
 
@@ -822,8 +831,9 @@ process_pay_with_exchange (void *cls,
           "{s:s, s:I, s:o, s:o}",
           "hint",
           TALER_ErrorCode_get_hint (
-            TALER_EC_PAY_DENOMINATION_KEY_NOT_FOUND),
-          "code", TALER_EC_PAY_DENOMINATION_KEY_NOT_FOUND,
+            TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_DENOMINATION_KEY_NOT_FOUND),
+          "code",
+          TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_DENOMINATION_KEY_NOT_FOUND,
           "h_denom_pub", GNUNET_JSON_from_data_auto (&dc->h_denom),
           "exchange_keys", TALER_EXCHANGE_get_keys_raw (exchange_handle)));
       return;
@@ -881,8 +891,11 @@ process_pay_with_exchange (void *cls,
         TALER_MHD_make_json_pack (
           "{s:s, s:I, s:i}",
           "hint",
-          TALER_ErrorCode_get_hint (TALER_EC_PAY_COIN_SIGNATURE_INVALID),
-          "code", (json_int_t) TALER_EC_PAY_COIN_SIGNATURE_INVALID,
+          TALER_ErrorCode_get_hint (
+            TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_COIN_SIGNATURE_INVALID),
+          "code",
+          (json_int_t)
+          TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_COIN_SIGNATURE_INVALID,
           "coin_idx", i));
       return;
     }
@@ -920,7 +933,7 @@ find_next_exchange (struct PayContext *pc)
         GNUNET_break (0);
         resume_pay_with_error (pc,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_PAY_EXCHANGE_LOOKUP_FAILED,
+                               TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_EXCHANGE_LOOKUP_FAILED,
                                "Failed to lookup exchange by URL");
         return;
       }
@@ -1070,7 +1083,7 @@ check_payment_sufficient (struct PayContext *pc)
       /* Overflow in these amounts? Very strange. */
       resume_pay_with_error (pc,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_PAY_AMOUNT_OVERFLOW,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AMOUNT_OVERFLOW,
                              "Overflow adding up amounts");
     }
     if (1 ==
@@ -1080,7 +1093,7 @@ check_payment_sufficient (struct PayContext *pc)
       GNUNET_break_op (0);
       resume_pay_with_error (pc,
                              MHD_HTTP_BAD_REQUEST,
-                             TALER_EC_PAY_FEES_EXCEED_PAYMENT,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_FEES_EXCEED_PAYMENT,
                              "Deposit fees exceed coin's contribution");
       return false;
     }
@@ -1105,8 +1118,8 @@ check_payment_sufficient (struct PayContext *pc)
           GNUNET_break_op (0);
           resume_pay_with_error (pc,
                                  MHD_HTTP_PRECONDITION_FAILED,
-                                 TALER_EC_PAY_WIRE_FEE_CURRENCY_MISMATCH,
-                                 "exchange wire in different currency");
+                                 TALER_EC_GENERIC_CURRENCY_MISMATCH,
+                                 total_wire_fee.currency);
           return false;
         }
         if (0 >
@@ -1117,7 +1130,7 @@ check_payment_sufficient (struct PayContext *pc)
           GNUNET_break (0);
           resume_pay_with_error (pc,
                                  MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                 TALER_EC_PAY_EXCHANGE_WIRE_FEE_ADDITION_FAILED,
+                                 TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_EXCHANGE_WIRE_FEE_ADDITION_FAILED,
                                  "could not add exchange wire fee to total");
           return false;
         }
@@ -1152,8 +1165,8 @@ check_payment_sufficient (struct PayContext *pc)
   {
     resume_pay_with_error (pc,
                            MHD_HTTP_PRECONDITION_FAILED,
-                           TALER_EC_PAY_WIRE_FEE_CURRENCY_MISMATCH,
-                           "exchange wire does not match our currency");
+                           TALER_EC_GENERIC_CURRENCY_MISMATCH,
+                           total_wire_fee.currency);
     return false;
   }
 
@@ -1189,7 +1202,7 @@ check_payment_sufficient (struct PayContext *pc)
     GNUNET_break (0);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_AMOUNT_OVERFLOW,
+                           TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AMOUNT_OVERFLOW,
                            "Overflow adding up amounts");
     return false;
   }
@@ -1217,7 +1230,7 @@ check_payment_sufficient (struct PayContext *pc)
       GNUNET_break (0);
       resume_pay_with_error (pc,
                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                             TALER_EC_PAY_AMOUNT_OVERFLOW,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_AMOUNT_OVERFLOW,
                              "Overflow adding up amounts");
       return false;
     }
@@ -1241,7 +1254,7 @@ check_payment_sufficient (struct PayContext *pc)
     GNUNET_break (0);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_REFUNDS_EXCEED_PAYMENTS,
+                           TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_REFUNDS_EXCEED_PAYMENTS,
                            "refunded amount exceeds total payments");
     return false;
   }
@@ -1255,7 +1268,7 @@ check_payment_sufficient (struct PayContext *pc)
     {
       resume_pay_with_error (pc,
                              MHD_HTTP_PAYMENT_REQUIRED,
-                             TALER_EC_PAY_REFUNDED,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_REFUNDED,
                              "contract not paid up due to refunds");
     }
     else if (-1 < TALER_amount_cmp (&acc_amount,
@@ -1264,7 +1277,7 @@ check_payment_sufficient (struct PayContext *pc)
       GNUNET_break_op (0);
       resume_pay_with_error (pc,
                              MHD_HTTP_NOT_ACCEPTABLE,
-                             TALER_EC_PAY_PAYMENT_INSUFFICIENT_DUE_TO_FEES,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_INSUFFICIENT_DUE_TO_FEES,
                              "contract not paid up due to fees (client may have calculated them badly)");
     }
     else
@@ -1272,7 +1285,7 @@ check_payment_sufficient (struct PayContext *pc)
       GNUNET_break_op (0);
       resume_pay_with_error (pc,
                              MHD_HTTP_NOT_ACCEPTABLE,
-                             TALER_EC_PAY_PAYMENT_INSUFFICIENT,
+                             TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_PAYMENT_INSUFFICIENT,
                              "payment insufficient");
     }
     return false;
@@ -1295,8 +1308,8 @@ begin_transaction (struct PayContext *pc)
     GNUNET_break (0);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_STORE_TRANSACTION_ERROR,
-                           "Soft merchant database error: retry counter exceeded");
+                           TALER_EC_GENERIC_DB_SOFT_FAILURE,
+                           NULL);
     return;
   }
   GNUNET_assert (GNUNET_YES == pc->suspended);
@@ -1326,8 +1339,8 @@ begin_transaction (struct PayContext *pc)
     GNUNET_break (0);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_FETCH_TRANSACTION_ERROR,
-                           "Merchant database error (could not begin transaction)");
+                           TALER_EC_GENERIC_DB_START_FAILED,
+                           NULL);
     return;
   }
 
@@ -1349,8 +1362,8 @@ begin_transaction (struct PayContext *pc)
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_FETCH_TRANSACTION_ERROR,
-                           "Merchant database error");
+                           TALER_EC_GENERIC_DB_FETCH_FAILED,
+                           "deposits");
     return;
   }
 
@@ -1372,8 +1385,8 @@ begin_transaction (struct PayContext *pc)
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_FETCH_TRANSACTION_ERROR,
-                           "Merchant database error checking for refunds");
+                           TALER_EC_GENERIC_DB_FETCH_FAILED,
+                           "lookup refunds");
     return;
   }
   refunded = (qs > 0);
@@ -1419,8 +1432,8 @@ begin_transaction (struct PayContext *pc)
     }
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_STORE_PAYMENTS_ERROR,
-                           "Could not set contract to 'paid' in DB");
+                           TALER_EC_GENERIC_DB_STORE_FAILED,
+                           "mark contract paid");
     return;
   }
 
@@ -1437,8 +1450,8 @@ begin_transaction (struct PayContext *pc)
     }
     resume_pay_with_error (pc,
                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                           TALER_EC_PAY_DB_STORE_PAYMENTS_ERROR,
-                           "Database commit mark proposal as 'paid' failed");
+                           TALER_EC_GENERIC_DB_COMMIT_FAILED,
+                           NULL);
     return;
   }
 
@@ -1489,7 +1502,7 @@ begin_transaction (struct PayContext *pc)
         GNUNET_break (0);
         resume_pay_with_error (pc,
                                MHD_HTTP_INTERNAL_SERVER_ERROR,
-                               TALER_EC_JSON_ALLOCATION_FAILURE,
+                               TALER_EC_GENERIC_JSON_ALLOCATION_FAILURE,
                                "Could not build final response");
         return;
       }
@@ -1562,7 +1575,7 @@ parse_pay (struct MHD_Connection *connection,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PAY_COINS_ARRAY_EMPTY,
+                                         TALER_EC_GENERIC_PARAMETER_MISSING,
                                          "'coins' array is empty or not even an array");
     }
 
@@ -1641,8 +1654,8 @@ parse_pay (struct MHD_Connection *connection,
       return (MHD_YES ==
               TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                          TALER_EC_PAY_DB_FETCH_PAY_ERROR,
-                                          NULL))
+                                          TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                          "contract terms"))
              ? GNUNET_NO
              : GNUNET_SYSERR;
     }
@@ -1651,7 +1664,7 @@ parse_pay (struct MHD_Connection *connection,
       return (MHD_YES ==
               TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_NOT_FOUND,
-                                          TALER_EC_PAY_PROPOSAL_NOT_FOUND,
+                                          TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                           pc->order_id))
              ? GNUNET_NO
              : GNUNET_SYSERR;
@@ -1667,7 +1680,7 @@ parse_pay (struct MHD_Connection *connection,
       return (MHD_YES ==
               TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                          TALER_EC_PAY_FAILED_COMPUTE_PROPOSAL_HASH,
+                                          TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                           NULL))
              ? GNUNET_NO
              : GNUNET_SYSERR;
@@ -1687,7 +1700,7 @@ parse_pay (struct MHD_Connection *connection,
       return (MHD_YES ==
               TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                          TALER_EC_PAY_MERCHANT_FIELD_MISSING,
+                                          TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_MERCHANT_FIELD_MISSING,
                                           NULL))
              ? GNUNET_NO
              : GNUNET_SYSERR;
@@ -1742,7 +1755,7 @@ parse_pay (struct MHD_Connection *connection,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PAY_REFUND_DEADLINE_PAST_WIRE_TRANSFER_DEADLINE,
+                                         TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_REFUND_DEADLINE_PAST_WIRE_TRANSFER_DEADLINE,
                                          NULL);
     }
 
@@ -1753,7 +1766,7 @@ parse_pay (struct MHD_Connection *connection,
       return (MHD_YES ==
               TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_GONE,
-                                          TALER_EC_PAY_OFFER_EXPIRED,
+                                          TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_OFFER_EXPIRED,
                                           NULL))
              ? GNUNET_NO
              : GNUNET_SYSERR;
@@ -1773,7 +1786,7 @@ parse_pay (struct MHD_Connection *connection,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PAY_WIRE_HASH_UNKNOWN,
+                                         TALER_EC_MERCHANT_POST_ORDERS_ID_PAY_WIRE_HASH_UNKNOWN,
                                          NULL);
     }
     pc->wm = wm;
@@ -1803,9 +1816,9 @@ handle_pay_timeout (void *cls)
     pc->fo = NULL;
   }
   resume_pay_with_error (pc,
-                         MHD_HTTP_REQUEST_TIMEOUT,
-                         TALER_EC_PAY_EXCHANGE_TIMEOUT,
-                         "likely the exchange did not reply quickly enough");
+                         MHD_HTTP_GATEWAY_TIMEOUT,
+                         TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT,
+                         NULL);
 }
 
 
diff --git a/src/backend/taler-merchant-httpd_post-orders-ID-refund.c b/src/backend/taler-merchant-httpd_post-orders-ID-refund.c
index cc12dc03..8c445680 100644
--- a/src/backend/taler-merchant-httpd_post-orders-ID-refund.c
+++ b/src/backend/taler-merchant-httpd_post-orders-ID-refund.c
@@ -130,8 +130,7 @@ struct PostRefundData
 {
 
   /**
-   * Hashed version of contract terms. All zeros if
-   * not provided.
+   * Hashed version of contract terms. All zeros if not provided.
    */
   struct GNUNET_HashCode h_contract_terms;
 
@@ -215,6 +214,11 @@ struct PostRefundData
   enum TALER_ErrorCode ec;
 
   /**
+   * HTTP status to use for the reply, 0 if not yet known.
+   */
+  unsigned int http_status;
+
+  /**
    * Set to true if we are dealing with an unclaimed order
    * (and thus @e h_contract_terms is not set, and certain
    * DB queries will not work).
@@ -340,7 +344,8 @@ exchange_operations_pending (struct PostRefundData *prd)
 static void
 check_resume_prd (struct PostRefundData *prd)
 {
-  if (exchange_operations_pending (prd))
+  if ( (TALER_EC_NONE == prd->ec) &&
+       exchange_operations_pending (prd) )
     return;
   GNUNET_CONTAINER_DLL_remove (prd_head,
                                prd_tail,
@@ -423,25 +428,34 @@ exchange_found_cb (void *cls,
                    bool exchange_trusted)
 {
   struct CoinRefund *cr = cls;
+  struct PostRefundData *prd = cr->prd;
 
   (void) payto_uri;
+  (void) wire_fee;
+  (void) exchange_trusted;
   cr->fo = NULL;
-  if (TALER_EC_NONE == hr->ec)
+  if (NULL == hr)
   {
-    cr->rh = TALER_EXCHANGE_refund (eh,
-                                    &cr->refund_amount,
-                                    &cr->prd->h_contract_terms,
-                                    &cr->coin_pub,
-                                    cr->rtransaction_id,
-                                    &cr->prd->hc->instance->merchant_priv,
-                                    &refund_cb,
-                                    cr);
+    prd->http_status = MHD_HTTP_GATEWAY_TIMEOUT;
+    prd->ec = TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT;
+    check_resume_prd (prd);
     return;
   }
-  cr->exchange_status = hr->http_status;
-  cr->exchange_code = hr->ec;
-  cr->exchange_reply = json_incref ((json_t*) hr->reply);
-  check_resume_prd (cr->prd);
+  if (NULL == eh)
+  {
+    prd->http_status = MHD_HTTP_BAD_GATEWAY;
+    prd->ec = TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE;
+    check_resume_prd (prd);
+    return;
+  }
+  cr->rh = TALER_EXCHANGE_refund (eh,
+                                  &cr->refund_amount,
+                                  &prd->h_contract_terms,
+                                  &cr->coin_pub,
+                                  cr->rtransaction_id,
+                                  &prd->hc->instance->merchant_priv,
+                                  &refund_cb,
+                                  cr);
 }
 
 
@@ -569,16 +583,16 @@ TMH_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
         GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
-                                           NULL);
+                                           TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                           "contract terms");
       }
       if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
       {
         json_decref (contract_terms);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_NOT_FOUND,
-                                           TALER_EC_GET_ORDERS_ORDER_NOT_FOUND,
-                                           NULL);
+                                           TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
+                                           hc->infix);
       }
       {
         struct GNUNET_HashCode h_contract_terms;
@@ -590,21 +604,50 @@ TMH_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
           json_decref (contract_terms);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                             TALER_EC_GET_ORDERS_FAILED_COMPUTE_PROPOSAL_HASH,
+                                             TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                              NULL);
         }
         json_decref (contract_terms);
         if (0 != GNUNET_memcmp (&h_contract_terms,
                                 &prd->h_contract_terms))
         {
-          return TALER_MHD_reply_with_error (connection,
-                                             MHD_HTTP_FORBIDDEN,
-                                             TALER_EC_GET_ORDER_WRONG_CONTRACT,
-                                             NULL);
+          return TALER_MHD_reply_with_error (
+            connection,
+            MHD_HTTP_FORBIDDEN,
+            TALER_EC_MERCHANT_GENERIC_CONTRACT_HASH_DOES_NOT_MATCH_ORDER,
+            NULL);
         }
       }
     }
   }
+
+  if (TALER_EC_NONE != prd->ec)
+  {
+    GNUNET_break (0 != prd->http_status);
+    /* kill pending coin refund operations immediately, just to be
+       extra sure they don't modify 'prd' after we already created
+       a reply (this might not be needed, but feels safer). */
+    for (struct CoinRefund *cr = prd->cr_head;
+         NULL != cr;
+         cr = cr->next)
+    {
+      if (NULL != cr->fo)
+      {
+        TMH_EXCHANGES_find_exchange_cancel (cr->fo);
+        cr->fo = NULL;
+      }
+      if (NULL != cr->rh)
+      {
+        TALER_EXCHANGE_refund_cancel (cr->rh);
+        cr->rh = NULL;
+      }
+    }
+    return TALER_MHD_reply_with_error (connection,
+                                       prd->http_status,
+                                       prd->ec,
+                                       NULL);
+  }
+
   {
     GNUNET_assert (GNUNET_OK == TALER_amount_get_zero (TMH_currency,
                                                        &prd->refund_amount));
@@ -618,8 +661,8 @@ TMH_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "detailed refunds");
     }
   }
 
@@ -641,8 +684,8 @@ TMH_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
     case GNUNET_DB_STATUS_SOFT_ERROR:
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "refund proof");
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
       if (NULL == cr->exchange_reply)
       {
diff --git a/src/backend/taler-merchant-httpd_post-tips-ID-pickup.c b/src/backend/taler-merchant-httpd_post-tips-ID-pickup.c
index 79c58632..29b8f13e 100644
--- a/src/backend/taler-merchant-httpd_post-tips-ID-pickup.c
+++ b/src/backend/taler-merchant-httpd_post-tips-ID-pickup.c
@@ -292,7 +292,7 @@ withdraw_cb (void *cls,
     pc->response =
       TALER_MHD_make_json_pack (
         "{s:I, s:I, s:I, s:O}",
-        "code", (json_int_t) TALER_EC_TIP_PICKUP_EXCHANGE_ERROR,
+        "code", (json_int_t) TALER_EC_MERCHANT_TIP_PICKUP_EXCHANGE_ERROR,
         "exchange_code", (json_int_t) hr->ec,
         "exchange_http_status", (json_int_t) hr->http_status,
         "exchange_reply", hr->reply);
@@ -309,8 +309,8 @@ withdraw_cb (void *cls,
     stop_operations (pc);
     pc->http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
     pc->response = TALER_MHD_make_error (
-      TALER_EC_TIP_PICKUP_DB_STORE_HARD_ERROR,
-      "Could not store blind signature in DB");
+      TALER_EC_GENERIC_DB_STORE_FAILED,
+      "blind signature");
     MHD_resume_connection (pc->connection);
     TMH_trigger_daemon ();   /* we resumed, kick MHD */
     return;
@@ -348,17 +348,37 @@ do_withdraw (void *cls,
   struct PickupContext *pc = po->pc;
 
   po->fo = NULL;
+  if (NULL == hr)
+  {
+    stop_operations (pc);
+    GNUNET_CONTAINER_DLL_remove (pc->po_head,
+                                 pc->po_tail,
+                                 po);
+    pc->http_status = MHD_HTTP_GATEWAY_TIMEOUT;
+    pc->response = TALER_MHD_make_json_pack (
+      "{s:s, s:I}",
+      "hint",
+      TALER_ErrorCode_get_hint (
+        TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT),
+      "code",
+      (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT);
+    MHD_resume_connection (pc->connection);
+    TMH_trigger_daemon ();   /* we resumed, kick MHD */
+    return;
+  }
   if (NULL == eh)
   {
     stop_operations (pc);
     GNUNET_CONTAINER_DLL_remove (pc->po_head,
                                  pc->po_tail,
                                  po);
-    pc->http_status = MHD_HTTP_FAILED_DEPENDENCY;
+    pc->http_status = MHD_HTTP_BAD_GATEWAY;
     pc->response =
       TALER_MHD_make_json_pack (
-        "{s:I, s:I, s:I, s:O}",
-        "code", (json_int_t) TALER_EC_TIP_PICKUP_CONTACT_EXCHANGE_ERROR,
+        "{s:s, s:I, s:I, s:I, s:O?}",
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE),
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE,
         "exchange_code", (json_int_t) hr->ec,
         "exchange_http_status", (json_int_t) hr->http_status,
         "exchange_reply", hr->reply);
@@ -422,10 +442,10 @@ do_timeout (void *cls)
 
   pc->tt = NULL;
   stop_operations (pc);
-  pc->http_status = MHD_HTTP_REQUEST_TIMEOUT;
+  pc->http_status = MHD_HTTP_GATEWAY_TIMEOUT;
   pc->response =  TALER_MHD_make_error (
-    TALER_EC_TIP_PICKUP_EXCHANGE_TIMEOUT,
-    "Timeout trying to withdraw from exchange (try again later)");
+    TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT,
+    NULL);
   MHD_resume_connection (pc->connection);
   TMH_trigger_daemon ();   /* we resumed, kick MHD */
 }
@@ -457,14 +477,43 @@ compute_total_requested (void *cls,
 
   pc->fo = NULL;
   stop_operations (pc); /* stops timeout job */
-  if ( (NULL == eh) ||
-       (NULL == (keys = TALER_EXCHANGE_get_keys (eh))) )
+  if (NULL == hr)
   {
-    pc->http_status = MHD_HTTP_FAILED_DEPENDENCY;
+    pc->http_status = MHD_HTTP_GATEWAY_TIMEOUT;
+    pc->response = TALER_MHD_make_json_pack (
+      "{s:I, s:s}",
+      "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT,
+      "hint", TALER_ErrorCode_get_hint (
+        TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT));
+    MHD_resume_connection (pc->connection);
+    TMH_trigger_daemon ();   /* we resumed, kick MHD */
+    return;
+  }
+  if (NULL == eh)
+  {
+    pc->http_status = MHD_HTTP_BAD_GATEWAY;
     pc->response =
       TALER_MHD_make_json_pack (
-        "{s:I, s:I, s:I, s:O}",
-        "code", (json_int_t) TALER_EC_TIP_PICKUP_EXCHANGE_KEYS_ERROR,
+        "{s:I, s:s, s:I, s:I, s:O}",
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE,
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE),
+        "exchange_code", (json_int_t) hr->ec,
+        "exchange_http_status", (json_int_t) hr->http_status,
+        "exchange_reply", hr->reply);
+    MHD_resume_connection (pc->connection);
+    TMH_trigger_daemon ();   /* we resumed, kick MHD */
+    return;
+  }
+  if (NULL == (keys = TALER_EXCHANGE_get_keys (eh)))
+  {
+    pc->http_status = MHD_HTTP_BAD_GATEWAY;
+    pc->response =
+      TALER_MHD_make_json_pack (
+        "{s:I, s:s, s:I, s:I, s:O}",
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE,
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE),
         "exchange_code", (json_int_t) hr->ec,
         "exchange_http_status", (json_int_t) hr->http_status,
         "exchange_reply", hr->reply);
@@ -488,7 +537,8 @@ compute_total_requested (void *cls,
       pc->response =
         TALER_MHD_make_json_pack (
           "{s:I, s:I, s:I, s:O}",
-          "code", (json_int_t) TALER_EC_TIP_PICKUP_DENOMINATION_UNKNOWN,
+          "code",
+          (json_int_t) TALER_EC_MERCHANT_TIP_PICKUP_DENOMINATION_UNKNOWN,
           "exchange_code", (json_int_t) hr->ec,
           "exchange_http_status", (json_int_t) hr->http_status,
           "exchange_reply", hr->reply);
@@ -507,7 +557,7 @@ compute_total_requested (void *cls,
     {
       pc->http_status = MHD_HTTP_BAD_REQUEST;
       pc->response =
-        TALER_MHD_make_error (TALER_EC_TIP_PICKUP_SUMMATION_FAILED,
+        TALER_MHD_make_error (TALER_EC_MERCHANT_TIP_PICKUP_SUMMATION_FAILED,
                               "Could not add up values to compute pickup total");
       MHD_resume_connection (pc->connection);
       TMH_trigger_daemon ();   /* we resumed, kick MHD */
@@ -538,20 +588,20 @@ reply_lookup_tip_failed (struct MHD_Connection *connection,
   switch (qs)
   {
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-    ec = TALER_EC_TIP_PICKUP_TIP_ID_UNKNOWN;
+    ec = TALER_EC_MERCHANT_GENERIC_TIP_ID_UNKNOWN;
     response_code = MHD_HTTP_NOT_FOUND;
     break;
   case GNUNET_DB_STATUS_SOFT_ERROR:
-    ec = TALER_EC_TIP_PICKUP_DB_ERROR_SOFT;
+    ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
     response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
     break;
   case GNUNET_DB_STATUS_HARD_ERROR:
-    ec = TALER_EC_TIP_PICKUP_DB_ERROR_HARD;
+    ec = TALER_EC_GENERIC_DB_COMMIT_FAILED;
     response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
     break;
   default:
     GNUNET_break (0);
-    ec = TALER_EC_INTERNAL_LOGIC_ERROR;
+    ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
     response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
     break;
   }
@@ -604,7 +654,7 @@ TMH_post_tips_ID_pickup (const struct TMH_RequestHandler *rh,
       GNUNET_break_op (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          hc->infix);
     }
 
@@ -632,7 +682,7 @@ TMH_post_tips_ID_pickup (const struct TMH_RequestHandler *rh,
       json_decref (planchets);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "planchets");
     }
 
@@ -735,7 +785,7 @@ RETRY:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_TIP_PICKUP_DB_ERROR_SOFT,
+                                       TALER_EC_GENERIC_DB_SOFT_FAILURE,
                                        NULL);
   }
   if (GNUNET_OK !=
@@ -745,7 +795,7 @@ RETRY:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_TIP_PICKUP_DB_ERROR_HARD,
+                                       TALER_EC_GENERIC_DB_START_FAILED,
                                        NULL);
   }
   {
@@ -827,12 +877,12 @@ RETRY:
         goto RETRY;
         break;
       case GNUNET_DB_STATUS_HARD_ERROR:
-        ec = TALER_EC_TIP_PICKUP_DB_ERROR_HARD;
+        ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
         response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
         break;
       default:
         GNUNET_break (0);
-        ec = TALER_EC_INTERNAL_LOGIC_ERROR;
+        ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
         response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
         break;
       }
@@ -861,7 +911,7 @@ RETRY:
     TMH_db->rollback (TMH_db->cls);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_GONE,
-                                       TALER_EC_TIP_PICKUP_HAS_EXPIRED,
+                                       TALER_EC_MERCHANT_TIP_PICKUP_HAS_EXPIRED,
                                        hc->infix);
   }
   if (0 >
@@ -873,8 +923,8 @@ RETRY:
     TMH_db->rollback (TMH_db->cls);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_LOGIC_ERROR,
-                                       hc->infix);
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                                       "picked up amount exceeds authorized amount");
   }
 
   if (0 >
@@ -885,7 +935,7 @@ RETRY:
     TMH_db->rollback (TMH_db->cls);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_TIP_PICKUP_AMOUNT_EXCEEDS_TIP_REMAINING,
+                                       TALER_EC_MERCHANT_TIP_PICKUP_AMOUNT_EXCEEDS_TIP_REMAINING,
                                        hc->infix);
   }
 
@@ -906,8 +956,8 @@ RETRY:
       goto RETRY;
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_TIP_PICKUP_DB_STORE_HARD_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
+                                       "pickup");
   }
   qs = TMH_db->commit (TMH_db->cls);
   if (qs < 0)
@@ -917,7 +967,7 @@ RETRY:
       goto RETRY;
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_TIP_PICKUP_DB_STORE_HARD_ERROR,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   }
   MHD_suspend_connection (connection);
diff --git a/src/backend/taler-merchant-httpd_private-delete-instances-ID.c b/src/backend/taler-merchant-httpd_private-delete-instances-ID.c
index c7432f04..1b1184cf 100644
--- a/src/backend/taler-merchant-httpd_private-delete-instances-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-instances-ID.c
@@ -57,18 +57,18 @@ TMH_private_delete_instances_ID (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_DELETE_INSTANCES_ID_DB_HARD_FAILURE,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
+                                       "delete private key");
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        NULL);
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_DELETE_INSTANCES_ID_NO_SUCH_INSTANCE,
+                                       TALER_EC_MERCHANT_GENERIC_INSTANCE_UNKNOWN,
                                        ( (NULL != purge) &&
                                          (0 == strcmp (purge,
                                                        "yes")) )
diff --git a/src/backend/taler-merchant-httpd_private-delete-orders-ID.c b/src/backend/taler-merchant-httpd_private-delete-orders-ID.c
index aadcb77e..057b45c3 100644
--- a/src/backend/taler-merchant-httpd_private-delete-orders-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-orders-ID.c
@@ -53,13 +53,13 @@ TMH_private_delete_orders_ID (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_ORDERS_DELETE_DB_HARD_FAILURE,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        NULL);
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     {
@@ -85,11 +85,11 @@ TMH_private_delete_orders_ID (const struct TMH_RequestHandler *rh,
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_ORDERS_DELETE_NO_SUCH_ORDER,
+                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                          hc->infix);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_CONFLICT,
-                                       TALER_EC_ORDERS_DELETE_AWAITING_PAYMENT,
+                                       TALER_EC_MERCHANT_PRIVATE_DELETE_ORDERS_AWAITING_PAYMENT,
                                        hc->infix);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
diff --git a/src/backend/taler-merchant-httpd_private-delete-products-ID.c b/src/backend/taler-merchant-httpd_private-delete-products-ID.c
index 054cf3a8..2d17bafc 100644
--- a/src/backend/taler-merchant-httpd_private-delete-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-products-ID.c
@@ -48,13 +48,13 @@ TMH_private_delete_products_ID (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_PRODUCTS_DELETE_DB_HARD_FAILURE,
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        NULL);
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     qs = TMH_db->lookup_product (TMH_db->cls,
@@ -64,12 +64,13 @@ TMH_private_delete_products_ID (const struct TMH_RequestHandler *rh,
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_PRODUCTS_DELETE_NO_SUCH_PRODUCT,
+                                         TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
                                          hc->infix);
-    return TALER_MHD_reply_with_error (connection,
-                                       MHD_HTTP_CONFLICT,
-                                       TALER_EC_PRODUCTS_DELETE_CONFLICTING_LOCK,
-                                       hc->infix);
+    return TALER_MHD_reply_with_error (
+      connection,
+      MHD_HTTP_CONFLICT,
+      TALER_EC_MERCHANT_PRIVATE_DELETE_PRODUCTS_CONFLICTING_LOCK,
+      hc->infix);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
                                    MHD_HTTP_NO_CONTENT,
diff --git a/src/backend/taler-merchant-httpd_private-delete-reserves-ID.c b/src/backend/taler-merchant-httpd_private-delete-reserves-ID.c
index 86d53327..96483384 100644
--- a/src/backend/taler-merchant-httpd_private-delete-reserves-ID.c
+++ b/src/backend/taler-merchant-httpd_private-delete-reserves-ID.c
@@ -50,7 +50,7 @@ TMH_private_delete_reserves_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_RESERVES_INVALID_RESERVE_PUB,
+                                       TALER_EC_MERCHANT_GENERIC_RESERVE_PUB_MALFORMED,
                                        hc->infix);
   }
   purge = MHD_lookup_connection_value (connection,
@@ -72,18 +72,18 @@ TMH_private_delete_reserves_ID (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_RESERVES_DELETE_DB_HARD_FAILURE,
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_DB_SOFT_FAILURE,
                                        "Serialization error for single SQL statement");
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_RESERVES_DELETE_NO_SUCH_RESERVE,
+                                       TALER_EC_MERCHANT_PRIVATE_DELETE_RESERVES_NO_SUCH_RESERVE,
                                        hc->infix);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
diff --git a/src/backend/taler-merchant-httpd_private-get-orders-ID.c b/src/backend/taler-merchant-httpd_private-get-orders-ID.c
index 9f0b9fef..6d4d625c 100644
--- a/src/backend/taler-merchant-httpd_private-get-orders-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-orders-ID.c
@@ -376,7 +376,7 @@ exchange_timeout_cb (void *cls)
   gorc->tt = NULL;
   gorc_resume (gorc,
                MHD_HTTP_REQUEST_TIMEOUT,
-               TALER_EC_GET_ORDERS_EXCHANGE_TIMEOUT);
+               TALER_EC_GENERIC_TIMEOUT);
 }
 
 
@@ -401,7 +401,7 @@ deposit_get_cb (void *cls,
   if (NULL == dd)
   {
     gorc_report (gorc,
-                 TALER_EC_GET_ORDERS_EXCHANGE_TRACKING_FAILURE,
+                 TALER_EC_MERCHANT_GET_ORDERS_EXCHANGE_TRACKING_FAILURE,
                  &tq->coin_pub,
                  hr);
     GNUNET_free (tq);
@@ -421,7 +421,7 @@ deposit_get_cb (void *cls,
     if (qs < 0)
     {
       gorc_report (gorc,
-                   TALER_EC_GET_ORDERS_DB_STORE_TRACKING_FAILURE,
+                   TALER_EC_GENERIC_DB_STORE_FAILED,
                    &tq->coin_pub,
                    NULL);
       GNUNET_free (tq);
@@ -438,7 +438,7 @@ deposit_get_cb (void *cls,
                           &dd->coin_contribution))
     {
       gorc_report (gorc,
-                   TALER_EC_GET_ORDERS_AMOUNT_ARITHMETIC_FAILURE,
+                   TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_ID_AMOUNT_ARITHMETIC_FAILURE,
                    &tq->coin_pub,
                    NULL);
       GNUNET_free (tq);
@@ -454,7 +454,7 @@ deposit_get_cb (void *cls,
                           &tq->deposit_fee))
     {
       gorc_report (gorc,
-                   TALER_EC_GET_ORDERS_AMOUNT_ARITHMETIC_FAILURE,
+                   TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_ID_AMOUNT_ARITHMETIC_FAILURE,
                    &tq->coin_pub,
                    NULL);
       GNUNET_free (tq);
@@ -506,6 +506,18 @@ exchange_found_cb (void *cls,
   struct GetOrderRequestContext *gorc = tq->gorc;
 
   tq->fo = NULL;
+  if (NULL == hr)
+  {
+    /* failed */
+    GNUNET_CONTAINER_DLL_remove (gorc->tq_head,
+                                 gorc->tq_tail,
+                                 tq);
+    GNUNET_free (tq);
+    gorc_resume (gorc,
+                 MHD_HTTP_GATEWAY_TIMEOUT,
+                 TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT);
+    return;
+  }
   if (NULL == eh)
   {
     /* failed */
@@ -516,8 +528,8 @@ exchange_found_cb (void *cls,
     gorc->exchange_hc = hr->http_status;
     gorc->exchange_ec = hr->ec;
     gorc_resume (gorc,
-                 MHD_HTTP_FAILED_DEPENDENCY,
-                 TALER_EC_GET_ORDERS_EXCHANGE_LOOKUP_FAILURE);
+                 MHD_HTTP_BAD_GATEWAY,
+                 TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE);
     return;
   }
   tq->dgh = TALER_EXCHANGE_deposits_get (eh,
@@ -535,7 +547,7 @@ exchange_found_cb (void *cls,
     GNUNET_free (tq);
     gorc_resume (gorc,
                  MHD_HTTP_INTERNAL_SERVER_ERROR,
-                 TALER_EC_GET_ORDERS_EXCHANGE_REQUEST_FAILURE);
+                 TALER_EC_MERCHANT_GET_ORDERS_ID_EXCHANGE_REQUEST_FAILURE);
   }
 }
 
@@ -587,7 +599,7 @@ deposit_cb (void *cls,
   {
     gorc_resume (gorc,
                  MHD_HTTP_INTERNAL_SERVER_ERROR,
-                 TALER_EC_GET_ORDERS_EXCHANGE_LOOKUP_START_FAILURE);
+                 TALER_EC_MERCHANT_GET_ORDERS_ID_EXCHANGE_LOOKUP_START_FAILURE);
   }
 }
 
@@ -783,7 +795,7 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
           GNUNET_break_op (0);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_PARAMETER_MALFORMED,
+                                             TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                              "timeout_ms must be non-negative number");
         }
         gorc->sc.long_poll_timeout
@@ -847,8 +859,8 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "contract terms");
   }
 
   {
@@ -873,14 +885,14 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "order");
     }
     if (order_only && (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs) )
     {
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_GET_ORDERS_ORDER_NOT_FOUND,
+                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                          hc->infix);
     }
     if (order_only)
@@ -909,7 +921,7 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       return TALER_MHD_reply_with_error (
         connection,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
-        TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
+        TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
         hc->infix);
     }
     if (0 !=
@@ -920,7 +932,7 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       return TALER_MHD_reply_with_error (
         connection,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
-        TALER_EC_GET_ORDERS_DB_FETCH_CONTRACT_TERMS_ERROR,
+        TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
         gorc->contract_amount.currency);
     }
   }
@@ -936,7 +948,7 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_FAILED_COMPUTE_PROPOSAL_HASH,
+                                         TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                          NULL);
     }
   }
@@ -973,8 +985,8 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_FETCH_PAYMENT_STATUS,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "payment status");
     }
   }
   if ( (! paid) &&
@@ -999,8 +1011,8 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_ORDERS_DB_FETCH_PAYMENT_STATUS,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "order by fulfillment");
     }
     if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
     {
@@ -1155,8 +1167,8 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_ORDERS_DB_FETCH_TRANSACTION_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "detailed refunds");
   }
 
   /* Generate final reply, including wire details if we have them */
@@ -1179,8 +1191,8 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PAY_DB_FETCH_TRANSACTION_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "transfer details");
     }
 
     if (! wired)
@@ -1195,10 +1207,11 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
                                  &gorc->refund_amount))
       {
         GNUNET_break (0);
-        return TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GET_ORDERS_CONTRACT_CONTENT_INVALID,
-                                           "refund exceeds contract value");
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_INTERNAL_SERVER_ERROR,
+          TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
+          "refund exceeds contract value");
       }
       if (0 >
           TALER_amount_subtract (&expect_total,
@@ -1206,10 +1219,11 @@ TMH_private_get_orders_ID (const struct TMH_RequestHandler *rh,
                                  &gorc->deposit_fees_total))
       {
         GNUNET_break (0);
-        return TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_GET_ORDERS_CONTRACT_CONTENT_INVALID,
-                                           "deposit fees exceed total minus refunds");
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_INTERNAL_SERVER_ERROR,
+          TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
+          "deposit fees exceed total minus refunds");
       }
       if (0 >=
           TALER_amount_cmp (&expect_total,
diff --git a/src/backend/taler-merchant-httpd_private-get-orders.c b/src/backend/taler-merchant-httpd_private-get-orders.c
index 8df4e69c..83ca09f9 100644
--- a/src/backend/taler-merchant-httpd_private-get-orders.c
+++ b/src/backend/taler-merchant-httpd_private-get-orders.c
@@ -272,7 +272,7 @@ add_order (void *cls,
     if (qs < 0)
     {
       GNUNET_break (0);
-      aos->result = TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_STATUS_DB_LOOKUP_ERROR;
+      aos->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
       return;
     }
   }
@@ -304,7 +304,7 @@ add_order (void *cls,
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
   {
     GNUNET_break (0);
-    aos->result = TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_CONTRACT_DB_LOOKUP_ERROR;
+    aos->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
     json_decref (contract_terms);
     return;
   }
@@ -329,7 +329,7 @@ add_order (void *cls,
                            NULL, NULL))
     {
       GNUNET_break (0);
-      aos->result = TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_PARSE_CONTRACT_ERROR;
+      aos->result = TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID;
       json_decref (contract_terms);
       return;
     }
@@ -350,8 +350,7 @@ add_order (void *cls,
       if (0 > qs)
       {
         GNUNET_break (0);
-        aos->result =
-          TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_REFUND_DB_LOOKUP_ERROR;
+        aos->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
         json_decref (contract_terms);
         return;
       }
@@ -497,7 +496,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                            &of.paid)) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "paid");
   if (! (TALER_arg_to_yna (connection,
                            "refunded",
@@ -505,7 +504,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                            &of.refunded)) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "refunded");
   if (! (TALER_arg_to_yna (connection,
                            "wired",
@@ -513,7 +512,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                            &of.wired)) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "wired");
   {
     const char *start_row_str;
@@ -537,7 +536,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "date");
       of.start_row = (uint64_t) ull;
     }
@@ -564,7 +563,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "delta");
       of.delta = (uint64_t) ll;
     }
@@ -589,7 +588,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                                                  &of.date))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "date");
     }
   }
@@ -615,7 +614,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "timeout_ms");
       of.timeout = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS,
                                                   ull);
@@ -636,8 +635,7 @@ TMH_private_get_orders (const struct TMH_RequestHandler *rh,
                                 aos);
     if (0 > qs)
     {
-      aos->result =
-        TALER_EC_MERCHANT_PRIVATE_GET_ORDERS_BY_FILTER_DB_LOOKUP_ERROR;
+      aos->result = TALER_EC_GENERIC_DB_FETCH_FAILED;
     }
     if (TALER_EC_NONE != aos->result)
     {
diff --git a/src/backend/taler-merchant-httpd_private-get-products-ID.c b/src/backend/taler-merchant-httpd_private-get-products-ID.c
index db5c223e..915b016c 100644
--- a/src/backend/taler-merchant-httpd_private-get-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-products-ID.c
@@ -50,14 +50,14 @@ TMH_private_get_products_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_PRODUCTS_DB_LOOKUP_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                                        NULL);
   }
   else if (0 == qs)
   {
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_GET_PRODUCTS_NOT_FOUND,
+                                       TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
                                        NULL);
   }
   {
diff --git a/src/backend/taler-merchant-httpd_private-get-products.c b/src/backend/taler-merchant-httpd_private-get-products.c
index fc07d311..9d8b40f8 100644
--- a/src/backend/taler-merchant-httpd_private-get-products.c
+++ b/src/backend/taler-merchant-httpd_private-get-products.c
@@ -72,7 +72,7 @@ TMH_private_get_products (const struct TMH_RequestHandler *rh,
     json_decref (pa);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_PRODUCTS_DB_LOOKUP_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                                        NULL);
   }
   return TALER_MHD_reply_json_pack (connection,
diff --git a/src/backend/taler-merchant-httpd_private-get-reserves-ID.c b/src/backend/taler-merchant-httpd_private-get-reserves-ID.c
index 9d7839f9..35d3707d 100644
--- a/src/backend/taler-merchant-httpd_private-get-reserves-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-reserves-ID.c
@@ -152,7 +152,7 @@ TMH_private_get_reserves_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        hc->infix);
   }
   {
@@ -187,20 +187,20 @@ TMH_private_get_reserves_ID (const struct TMH_RequestHandler *rh,
       switch (qs)
       {
       case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-        ec = TALER_EC_TIP_PICKUP_TIP_ID_UNKNOWN;
+        ec = TALER_EC_MERCHANT_GENERIC_TIP_ID_UNKNOWN;
         response_code = MHD_HTTP_NOT_FOUND;
         break;
       case GNUNET_DB_STATUS_SOFT_ERROR:
-        ec = TALER_EC_TIP_PICKUP_DB_ERROR_SOFT;
+        ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
         response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
         break;
       case GNUNET_DB_STATUS_HARD_ERROR:
-        ec = TALER_EC_TIP_PICKUP_DB_ERROR_HARD;
+        ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
         response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
         break;
       default:
         GNUNET_break (0);
-        ec = TALER_EC_INTERNAL_LOGIC_ERROR;
+        ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
         response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
         break;
       }
diff --git a/src/backend/taler-merchant-httpd_private-get-reserves.c b/src/backend/taler-merchant-httpd_private-get-reserves.c
index a495da4e..8b12afbe 100644
--- a/src/backend/taler-merchant-httpd_private-get-reserves.c
+++ b/src/backend/taler-merchant-httpd_private-get-reserves.c
@@ -107,7 +107,7 @@ TMH_private_get_reserves (const struct TMH_RequestHandler *rh,
   {
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "active");
   }
 
@@ -118,7 +118,7 @@ TMH_private_get_reserves (const struct TMH_RequestHandler *rh,
   {
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "failures");
   }
 
@@ -137,8 +137,8 @@ TMH_private_get_reserves (const struct TMH_RequestHandler *rh,
     json_decref (ra);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_GET_RESERVES_DB_LOOKUP_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "reserves");
   }
   return TALER_MHD_reply_json_pack (connection,
                                     MHD_HTTP_OK,
diff --git a/src/backend/taler-merchant-httpd_private-get-tips-ID.c b/src/backend/taler-merchant-httpd_private-get-tips-ID.c
index f1a3254c..7ebe6b9c 100644
--- a/src/backend/taler-merchant-httpd_private-get-tips-ID.c
+++ b/src/backend/taler-merchant-httpd_private-get-tips-ID.c
@@ -54,7 +54,7 @@ TMH_private_get_tips_ID (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        hc->infix);
   }
   {
@@ -87,20 +87,20 @@ TMH_private_get_tips_ID (const struct TMH_RequestHandler *rh,
     switch (qs)
     {
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
-      ec = TALER_EC_TIP_PICKUP_TIP_ID_UNKNOWN;
+      ec = TALER_EC_MERCHANT_GENERIC_TIP_ID_UNKNOWN;
       response_code = MHD_HTTP_NOT_FOUND;
       break;
     case GNUNET_DB_STATUS_SOFT_ERROR:
-      ec = TALER_EC_TIP_PICKUP_DB_ERROR_SOFT;
+      ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
       response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
       break;
     case GNUNET_DB_STATUS_HARD_ERROR:
-      ec = TALER_EC_TIP_PICKUP_DB_ERROR_HARD;
+      ec = TALER_EC_GENERIC_DB_COMMIT_FAILED;
       response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
       break;
     default:
       GNUNET_break (0);
-      ec = TALER_EC_INTERNAL_LOGIC_ERROR;
+      ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
       response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
       break;
     }
diff --git a/src/backend/taler-merchant-httpd_private-get-tips.c b/src/backend/taler-merchant-httpd_private-get-tips.c
index 4282ebe7..60e4900e 100644
--- a/src/backend/taler-merchant-httpd_private-get-tips.c
+++ b/src/backend/taler-merchant-httpd_private-get-tips.c
@@ -69,7 +69,7 @@ TMH_private_get_tips (const struct TMH_RequestHandler *rh,
                            &expired)) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "expired");
   {
     const char *limit_str;
@@ -93,7 +93,7 @@ TMH_private_get_tips (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "limit");
       limit = (uint64_t) ll;
     }
@@ -123,7 +123,7 @@ TMH_private_get_tips (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "offset");
       offset = (uint64_t) ull;
     }
@@ -145,8 +145,8 @@ TMH_private_get_tips (const struct TMH_RequestHandler *rh,
     json_decref (pa);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_ORDERS_GET_DB_LOOKUP_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                       "tips");
   }
 
   return TALER_MHD_reply_json_pack (connection,
diff --git a/src/backend/taler-merchant-httpd_private-get-transfers.c b/src/backend/taler-merchant-httpd_private-get-transfers.c
index ffff32be..3ac15d01 100644
--- a/src/backend/taler-merchant-httpd_private-get-transfers.c
+++ b/src/backend/taler-merchant-httpd_private-get-transfers.c
@@ -121,7 +121,7 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
                                                  &before)) )
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "before");
   }
   {
@@ -136,7 +136,7 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
                                                  &after)) )
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "after");
   }
   {
@@ -157,7 +157,7 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "limit");
       limit = (int64_t) l;
     }
@@ -180,7 +180,7 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
                   dummy))
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "offset");
       offset = (uint64_t) o;
     }
@@ -198,7 +198,7 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
                            &verified)) )
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "verified");
 
   TMH_db->preflight (TMH_db->cls);
@@ -226,8 +226,8 @@ TMH_private_get_transfers (const struct TMH_RequestHandler *rh,
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_GET_TRANSFERS_DB_FETCH_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "transfers");
     }
     return TALER_MHD_reply_json_pack (connection,
                                       MHD_HTTP_OK,
diff --git a/src/backend/taler-merchant-httpd_private-patch-instances-ID.c b/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
index 1534f62b..755e6f02 100644
--- a/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
+++ b/src/backend/taler-merchant-httpd_private-patch-instances-ID.c
@@ -104,7 +104,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
   if (! json_is_array (payto_uris))
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PATCH_INSTANCES_BAD_PAYTO_URIS,
+                                       TALER_EC_GENERIC_PAYTO_URI_MALFORMED,
                                        NULL);
   for (unsigned int i = 0; i<MAX_RETRIES; i++)
   {
@@ -129,7 +129,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_CONFLICT,
-                                         TALER_EC_PATCH_INSTANCES_BAD_CURRENCY,
+                                         TALER_EC_GENERIC_CURRENCY_MISMATCH,
                                          NULL);
     }
     if (GNUNET_OK !=
@@ -139,7 +139,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PATCH_INSTANCES_DB_START_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
                                          NULL);
     }
     /* Check for equality of settings */
@@ -207,7 +207,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
             GNUNET_assert (NULL == wm_head);
             return TALER_MHD_reply_with_error (connection,
                                                MHD_HTTP_BAD_REQUEST,
-                                               TALER_EC_POST_INSTANCES_BAD_PAYTO_URIS,
+                                               TALER_EC_GENERIC_PAYTO_URI_MALFORMED,
                                                NULL);
           }
           if ((0 == strcasecmp (uri,
@@ -221,7 +221,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
               GNUNET_assert (NULL == wm_head);
               return TALER_MHD_reply_with_error (connection,
                                                  MHD_HTTP_BAD_REQUEST,
-                                                 TALER_EC_POST_INSTANCES_BAD_PAYTO_URIS,
+                                                 TALER_EC_GENERIC_PAYTO_URI_MALFORMED,
                                                  str);
             }
             matches[i] = true;
@@ -292,7 +292,7 @@ TMH_private_patch_instances_ID (const struct TMH_RequestHandler *rh,
           GNUNET_JSON_parse_free (spec);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_POST_INSTANCES_BAD_PAYTO_URIS,
+                                             TALER_EC_GENERIC_PAYTO_URI_MALFORMED,
                                              ad.payto_uri);
         }
         wm->active = true;
@@ -336,7 +336,7 @@ giveup:
     GNUNET_JSON_parse_free (spec);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_PATCH_INSTANCES_DB_COMMIT_ERROR,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   }
   /* Deactivate existing wire methods that were removed above */
diff --git a/src/backend/taler-merchant-httpd_private-patch-orders-ID-forget.c b/src/backend/taler-merchant-httpd_private-patch-orders-ID-forget.c
index d9d8df49..494787ed 100644
--- a/src/backend/taler-merchant-httpd_private-patch-orders-ID-forget.c
+++ b/src/backend/taler-merchant-httpd_private-patch-orders-ID-forget.c
@@ -81,7 +81,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
     {
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_FORGET_ORDER_DB_START_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
                                          NULL);
     }
     qs = TMH_db->lookup_contract_terms (TMH_db->cls,
@@ -95,8 +95,8 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
       TMH_db->rollback (TMH_db->cls);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_ORDERS_CLAIM_HARD_DB_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "contract terms");
     case GNUNET_DB_STATUS_SOFT_ERROR:
       TMH_db->rollback (TMH_db->cls);
       continue;
@@ -104,7 +104,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
       TMH_db->rollback (TMH_db->cls);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_FORGET_ORDER_NOT_FOUND,
+                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                          order_id);
     case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
       GNUNET_assert (NULL != contract_terms);
@@ -138,7 +138,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
       json_decref (fields);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "fields");
     }
 
@@ -156,7 +156,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
           json_decref (fields);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_FORGET_PATH_SYNTAX_INCORRECT,
+                                             TALER_EC_MERCHANT_PRIVATE_PATCH_ORDERS_ID_FORGET_PATH_SYNTAX_INCORRECT,
                                              "field is not a string");
         }
         expand_status = TALER_JSON_expand_path (contract_terms,
@@ -171,7 +171,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
           json_decref (fields);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_CONFLICT,
-                                             TALER_EC_FORGET_PATH_NOT_FORGETTABLE,
+                                             TALER_EC_MERCHANT_PRIVATE_PATCH_ORDERS_ID_FORGET_PATH_NOT_FORGETTABLE,
                                              json_string_value (value));
         }
         if (GNUNET_SYSERR == expand_status)
@@ -182,7 +182,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
           json_decref (fields);
           return TALER_MHD_reply_with_error (connection,
                                              MHD_HTTP_BAD_REQUEST,
-                                             TALER_EC_FORGET_PATH_SYNTAX_INCORRECT,
+                                             TALER_EC_MERCHANT_PRIVATE_PATCH_ORDERS_ID_FORGET_PATH_SYNTAX_INCORRECT,
                                              json_string_value (value));
         }
       }
@@ -211,7 +211,7 @@ TMH_private_patch_orders_ID_forget (const struct TMH_RequestHandler *rh,
   {
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_FORGET_ORDER_DB_COMMIT_ERROR,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   }
 
diff --git a/src/backend/taler-merchant-httpd_private-patch-products-ID.c b/src/backend/taler-merchant-httpd_private-patch-products-ID.c
index 5fd3a1ef..dd989866 100644
--- a/src/backend/taler-merchant-httpd_private-patch-products-ID.c
+++ b/src/backend/taler-merchant-httpd_private-patch-products-ID.c
@@ -59,18 +59,18 @@ determine_cause (struct MHD_Connection *connection,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_PRODUCTS_PATCH_DB_COMMIT_HARD_ERROR,
+                                       TALER_EC_GENERIC_DB_FETCH_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        "unexpected serialization problem");
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_PRODUCTS_PATCH_UNKNOWN_PRODUCT,
+                                       TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
                                        product_id);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     break; /* do below */
@@ -79,13 +79,13 @@ determine_cause (struct MHD_Connection *connection,
   {
     enum TALER_ErrorCode ec;
 
-    ec = TALER_EC_INTERNAL_INVARIANT_FAILURE;
+    ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
     if (pdx.total_lost > pd->total_lost)
-      ec = TALER_EC_PRODUCTS_PATCH_TOTAL_LOST_REDUCED;
+      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_LOST_REDUCED;
     if (pdx.total_stock > pd->total_stock)
-      ec = TALER_EC_PRODUCTS_PATCH_TOTAL_STOCKED_REDUCED;
+      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_STOCKED_REDUCED;
     if (pd->total_stock - pdx.total_sold > pd->total_lost)
-      ec = TALER_EC_PRODUCTS_PATCH_TOTAL_LOST_EXCEEDS_STOCKS;
+      ec = TALER_EC_MERCHANT_PRIVATE_PATCH_PRODUCTS_TOTAL_LOST_EXCEEDS_STOCKS;
     GNUNET_free (pdx.description);
     json_decref (pdx.description_i18n);
     GNUNET_free (pdx.unit);
@@ -195,14 +195,14 @@ TMH_private_patch_products_ID (const struct TMH_RequestHandler *rh,
     case GNUNET_DB_STATUS_HARD_ERROR:
       ret = TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                        TALER_EC_PRODUCTS_PATCH_DB_COMMIT_HARD_ERROR,
+                                        TALER_EC_GENERIC_DB_STORE_FAILED,
                                         NULL);
       break;
     case GNUNET_DB_STATUS_SOFT_ERROR:
       GNUNET_break (0);
       ret = TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                        TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                        TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                         "unexpected serialization problem");
       break;
     case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
diff --git a/src/backend/taler-merchant-httpd_private-post-instances.c b/src/backend/taler-merchant-httpd_private-post-instances.c
index 1a9d2b27..1cd1a0bb 100644
--- a/src/backend/taler-merchant-httpd_private-post-instances.c
+++ b/src/backend/taler-merchant-httpd_private-post-instances.c
@@ -189,8 +189,8 @@ TMH_private_post_instances (const struct TMH_RequestHandler *rh,
     GNUNET_JSON_parse_free (spec);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_CONFLICT,
-                                       TALER_EC_POST_INSTANCES_BAD_CURRENCY,
-                                       NULL);
+                                       TALER_EC_GENERIC_CURRENCY_MISMATCH,
+                                       TMH_currency);
   }
 
   {
@@ -240,7 +240,7 @@ TMH_private_post_instances (const struct TMH_RequestHandler *rh,
         GNUNET_JSON_parse_free (spec);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_CONFLICT,
-                                           TALER_EC_POST_INSTANCES_ALREADY_EXISTS,
+                                           TALER_EC_MERCHANT_PRIVATE_POST_INSTANCES_ALREADY_EXISTS,
                                            is.id);
       }
     }
@@ -338,7 +338,7 @@ TMH_private_post_instances (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_POST_INSTANCES_BAD_PAYTO_URIS,
+                                         TALER_EC_GENERIC_PAYTO_URI_MALFORMED,
                                          NULL);
     }
   }
@@ -369,7 +369,7 @@ TMH_private_post_instances (const struct TMH_RequestHandler *rh,
         free_mi (mi);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_POST_INSTANCES_DB_START_ERROR,
+                                           TALER_EC_GENERIC_DB_START_FAILED,
                                            NULL);
       }
       qs = TMH_db->insert_instance (TMH_db->cls,
@@ -424,7 +424,7 @@ retry:
       free_mi (mi);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_POST_INSTANCES_DB_COMMIT_ERROR,
+                                         TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                          NULL);
     }
     /* Finally, also update our running process */
diff --git a/src/backend/taler-merchant-httpd_private-post-orders-ID-refund.c b/src/backend/taler-merchant-httpd_private-post-orders-ID-refund.c
index 59b82752..49bc1b6e 100644
--- a/src/backend/taler-merchant-httpd_private-post-orders-ID-refund.c
+++ b/src/backend/taler-merchant-httpd_private-post-orders-ID-refund.c
@@ -145,10 +145,11 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
         GNUNET_break (0);
         GNUNET_JSON_parse_free (spec);
         json_decref (contract_terms);
-        return TALER_MHD_reply_with_error (connection,
-                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_INTERNAL_LOGIC_ERROR,
-                                           "Failed to parse contract terms from DB");
+        return TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_INTERNAL_SERVER_ERROR,
+          TALER_EC_MERCHANT_GENERIC_DB_CONTRACT_CONTENT_INVALID,
+          "mandatory fields missing");
       }
       json_decref (contract_terms);
       if (timestamp.abs_value_us == refund_deadline.abs_value_us)
@@ -175,7 +176,7 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
     {
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_REFUND_ORDER_ID_UNKNOWN,
+                                         TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                          hc->infix);
     }
   }
@@ -202,7 +203,7 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_REFUND_STORE_DB_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
                                          NULL);
     }
     rs = TMH_db->increase_refund (TMH_db->cls,
@@ -242,13 +243,13 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
                 TALER_amount2s (&refund));
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_CONFLICT,
-                                       TALER_EC_REFUND_INCONSISTENT_AMOUNT,
+                                       TALER_EC_EXCHANGE_REFUND_INCONSISTENT_AMOUNT,
                                        "Amount above payment");
   case TALER_MERCHANTDB_RS_SOFT_ERROR:
   case TALER_MERCHANTDB_RS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_REFUND_MERCHANT_DB_COMMIT_ERROR,
+                                       TALER_EC_GENERIC_DB_COMMIT_FAILED,
                                        NULL);
   case TALER_MERCHANTDB_RS_NO_SUCH_ORDER:
     {
@@ -256,10 +257,11 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
          "lookup_contract_terms" at the beginning;
          so if we get 'no such order' here, it
          must be read as "no PAID order" */
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_CONFLICT,
-                                         TALER_EC_REFUND_ORDER_ID_UNPAID,
-                                         hc->infix);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_CONFLICT,
+        TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ID_REFUND_ORDER_UNPAID,
+        hc->infix);
     }
   case TALER_MERCHANTDB_RS_SUCCESS:
     {
@@ -276,7 +278,7 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
       {
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_NOT_FOUND,
-                                           TALER_EC_REFUND_ORDER_ID_UNKNOWN,
+                                           TALER_EC_MERCHANT_GENERIC_ORDER_UNKNOWN,
                                            hc->infix);
       }
       if (GNUNET_OK !=
@@ -287,7 +289,7 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
         json_decref (contract_terms);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_INTERNAL_LOGIC_ERROR,
+                                           TALER_EC_GENERIC_FAILED_COMPUTE_JSON_HASH,
                                            "Could not hash contract terms");
       }
       json_decref (contract_terms);
@@ -319,7 +321,7 @@ TMH_private_post_orders_ID_refund (const struct TMH_RequestHandler *rh,
       GNUNET_break (0);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_REFUND_DB_INCONSISTENT,
+                                         TALER_EC_GENERIC_DB_INVARIANT_FAILURE,
                                          NULL);
     }
     TMH_notify_order_change (hc->instance,
diff --git a/src/backend/taler-merchant-httpd_private-post-orders.c b/src/backend/taler-merchant-httpd_private-post-orders.c
index bac98d43..b0bfa30f 100644
--- a/src/backend/taler-merchant-httpd_private-post-orders.c
+++ b/src/backend/taler-merchant-httpd_private-post-orders.c
@@ -400,7 +400,7 @@ execute_order (struct MHD_Connection *connection,
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_CONFLICT,
-      TALER_EC_PROPOSAL_ORDER_BAD_CURRENCY,
+      TALER_EC_GENERIC_CURRENCY_MISMATCH,
       TMH_currency);
   }
 
@@ -415,7 +415,7 @@ execute_order (struct MHD_Connection *connection,
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_BAD_REQUEST,
-      TALER_EC_PARAMETER_MALFORMED,
+      TALER_EC_GENERIC_PARAMETER_MALFORMED,
       "order:wire_transfer_deadline;order:refund_deadline");
   }
 
@@ -426,7 +426,7 @@ execute_order (struct MHD_Connection *connection,
     GNUNET_JSON_parse_free (spec);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_PARAMETER_MALFORMED,
+                                       TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                        "order:products");
   }
 
@@ -477,10 +477,11 @@ execute_order (struct MHD_Connection *connection,
         /* This request is not idempotent */
         MHD_RESULT ret;
 
-        ret = TALER_MHD_reply_with_error (connection,
-                                          MHD_HTTP_CONFLICT,
-                                          TALER_EC_PROPOSAL_STORE_DB_ERROR_ALREADY_EXISTS,
-                                          order_id);
+        ret = TALER_MHD_reply_with_error (
+          connection,
+          MHD_HTTP_CONFLICT,
+          TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ALREADY_EXISTS,
+          order_id);
         GNUNET_JSON_parse_free (spec);
         return ret;
       }
@@ -515,7 +516,7 @@ execute_order (struct MHD_Connection *connection,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PROPOSAL_STORE_DB_ERROR_SOFT,
+                                         TALER_EC_GENERIC_DB_SOFT_FAILURE,
                                          NULL);
     }
 
@@ -523,10 +524,11 @@ execute_order (struct MHD_Connection *connection,
     {
       /* should be: contract (!) with same order ID
          already exists */
-      return TALER_MHD_reply_with_error (connection,
-                                         MHD_HTTP_CONFLICT,
-                                         TALER_EC_PROPOSAL_STORE_DB_ERROR_ALREADY_EXISTS,
-                                         order_id);
+      return TALER_MHD_reply_with_error (
+        connection,
+        MHD_HTTP_CONFLICT,
+        TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_ALREADY_EXISTS,
+        order_id);
     }
 
     /* If we have a product that has insufficient quantities,
@@ -563,7 +565,7 @@ execute_order (struct MHD_Connection *connection,
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
-      TALER_EC_PROPOSAL_STORE_DB_ERROR_HARD,
+      TALER_EC_GENERIC_DB_COMMIT_FAILED,
       NULL);
   }
   /* DB transaction succeeded, generate positive response */
@@ -696,7 +698,7 @@ patch_order (struct MHD_Connection *connection,
       return TALER_MHD_reply_with_error (
         connection,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
-        TALER_EC_PROPOSAL_NO_LOCALTIME,
+        TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_NO_LOCALTIME,
         NULL);
     }
     off = strftime (buf,
@@ -755,7 +757,7 @@ patch_order (struct MHD_Connection *connection,
 
   {
     struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();
-    
+
     (void) GNUNET_TIME_round_abs (&now);
     /* Add timestamp if it doesn't exist (or is zero) */
     if (0 == timestamp.abs_value_us)
@@ -767,7 +769,8 @@ patch_order (struct MHD_Connection *connection,
     }
 
     /* If no refund_deadline given, set one based on refund_delay.  */
-    if (GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us == refund_deadline.abs_value_us)
+    if (GNUNET_TIME_UNIT_FOREVER_ABS.abs_value_us ==
+        refund_deadline.abs_value_us)
     {
       struct GNUNET_TIME_Absolute rd =
         GNUNET_TIME_relative_to_absolute (refund_delay);
@@ -858,7 +861,7 @@ patch_order (struct MHD_Connection *connection,
     return TALER_MHD_reply_with_error (
       connection,
       MHD_HTTP_BAD_REQUEST,
-      TALER_EC_PROPOSAL_ORDER_PARSE_ERROR,
+      TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_PROPOSAL_PARSE_ERROR,
       "'merchant' field already set, but must be provided by backend");
   }
   else
@@ -986,7 +989,7 @@ add_payment_details (struct MHD_Connection *connection,
                 hc->instance->settings.id);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_PROPOSAL_INSTANCE_CONFIGURATION_LACKS_WIRE,
+                                       TALER_EC_MERCHANT_PRIVATE_POST_ORDERS_INSTANCE_CONFIGURATION_LACKS_WIRE,
                                        payment_target);
   }
   GNUNET_assert (0 ==
@@ -1067,23 +1070,23 @@ merge_inventory (struct MHD_Connection *connection,
                                    &pd);
       if (qs <= 0)
       {
-        enum TALER_ErrorCode ec = TALER_EC_INTERNAL_INVARIANT_FAILURE;
+        enum TALER_ErrorCode ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
         unsigned int http_status = 0;
 
         switch (qs)
         {
         case GNUNET_DB_STATUS_HARD_ERROR:
           http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
-          ec = TALER_EC_ORDERS_LOOKUP_PRODUCT_DB_HARD_FAILURE;
+          ec = TALER_EC_GENERIC_DB_FETCH_FAILED;
           break;
         case GNUNET_DB_STATUS_SOFT_ERROR:
           GNUNET_break (0);
           http_status = MHD_HTTP_INTERNAL_SERVER_ERROR;
-          ec = TALER_EC_ORDERS_LOOKUP_PRODUCT_DB_SOFT_FAILURE;
+          ec = TALER_EC_GENERIC_DB_SOFT_FAILURE;
           break;
         case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
           http_status = MHD_HTTP_NOT_FOUND;
-          ec = TALER_EC_ORDERS_LOOKUP_PRODUCT_NOT_FOUND;
+          ec = TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN;
           break;
         case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
           /* case listed to make compilers happy */
@@ -1253,7 +1256,7 @@ TMH_private_post_orders (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_ALLOCATION_FAILURE,
+                                         TALER_EC_GENERIC_ALLOCATION_FAILURE,
                                          "request body normalization for hashing");
     }
     /* We include the full request: JSON body and the create_token and
@@ -1278,7 +1281,7 @@ TMH_private_post_orders (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "inventory_products");
     }
     GNUNET_array_grow (ips,
@@ -1315,7 +1318,7 @@ TMH_private_post_orders (const struct TMH_RequestHandler *rh,
         GNUNET_JSON_parse_free (spec);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "inventory_products");
       }
     }
@@ -1332,7 +1335,7 @@ TMH_private_post_orders (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         TALER_EC_PARAMETER_MALFORMED,
+                                         TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                          "lock_uuids");
     }
     GNUNET_array_grow (uuids,
@@ -1370,7 +1373,7 @@ TMH_private_post_orders (const struct TMH_RequestHandler *rh,
         GNUNET_JSON_parse_free (spec);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_BAD_REQUEST,
-                                           TALER_EC_PARAMETER_MALFORMED,
+                                           TALER_EC_GENERIC_PARAMETER_MALFORMED,
                                            "lock_uuids");
       }
     }
diff --git a/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c b/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
index 6cb6650a..5a27b56f 100644
--- a/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
+++ b/src/backend/taler-merchant-httpd_private-post-products-ID-lock.c
@@ -81,13 +81,13 @@ TMH_private_post_products_ID_lock (const struct TMH_RequestHandler *rh,
   case GNUNET_DB_STATUS_HARD_ERROR:
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_PRODUCTS_PATCH_DB_COMMIT_HARD_ERROR,
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
                                        NULL);
   case GNUNET_DB_STATUS_SOFT_ERROR:
     GNUNET_break (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_INTERNAL_INVARIANT_FAILURE,
+                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                        "Serialization error for single-statment request");
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     qs = TMH_db->lookup_product (TMH_db->cls,
@@ -97,12 +97,12 @@ TMH_private_post_products_ID_lock (const struct TMH_RequestHandler *rh,
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_PRODUCTS_LOCK_UNKNOWN_PRODUCT,
+                                         TALER_EC_MERCHANT_GENERIC_PRODUCT_UNKNOWN,
                                          product_id);
     else
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_GONE,
-                                         TALER_EC_PRODUCTS_LOCK_INSUFFICIENT_STOCKS,
+                                         TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_LOCK_INSUFFICIENT_STOCKS,
                                          product_id);
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
     return TALER_MHD_reply_static (connection,
diff --git a/src/backend/taler-merchant-httpd_private-post-products.c b/src/backend/taler-merchant-httpd_private-post-products.c
index e77690bc..5b783519 100644
--- a/src/backend/taler-merchant-httpd_private-post-products.c
+++ b/src/backend/taler-merchant-httpd_private-post-products.c
@@ -136,7 +136,7 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
       GNUNET_JSON_parse_free (spec);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_PRODUCTS_POST_DB_START_ERROR,
+                                         TALER_EC_GENERIC_DB_START_FAILED,
                                          NULL);
     }
     qs = TMH_db->lookup_product (TMH_db->cls,
@@ -173,7 +173,7 @@ TMH_private_post_products (const struct TMH_RequestHandler *rh,
         GNUNET_JSON_parse_free (spec);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_CONFLICT,
-                                           TALER_EC_PRODUCTS_POST_CONFLICT_PRODUCT_EXISTS,
+                                           TALER_EC_MERCHANT_PRIVATE_POST_PRODUCTS_CONFLICT_PRODUCT_EXISTS,
                                            product_id);
       }
     }
@@ -200,8 +200,8 @@ retry:
       connection,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
       (GNUNET_DB_STATUS_SOFT_ERROR == qs)
-      ? TALER_EC_PRODUCTS_POST_DB_COMMIT_SOFT_ERROR
-      : TALER_EC_PRODUCTS_POST_DB_COMMIT_HARD_ERROR,
+      ? TALER_EC_GENERIC_DB_SOFT_FAILURE
+      : TALER_EC_GENERIC_DB_COMMIT_FAILED,
       NULL);
   return TALER_MHD_reply_static (connection,
                                  MHD_HTTP_NO_CONTENT,
diff --git a/src/backend/taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c b/src/backend/taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c
index fa17a0ec..04b40e32 100644
--- a/src/backend/taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c
+++ b/src/backend/taler-merchant-httpd_private-post-reserves-ID-authorize-tip.c
@@ -85,16 +85,16 @@ authorize_tip (const struct TMH_RequestHandler *rh,
 
     switch (ec)
     {
-    case TALER_EC_TIP_AUTHORIZE_INSUFFICIENT_FUNDS:
+    case TALER_EC_MERCHANT_PRIVATE_POST_TIP_AUTHORIZE_INSUFFICIENT_FUNDS:
       http_status = MHD_HTTP_PRECONDITION_FAILED;
       break;
-    case TALER_EC_TIP_AUTHORIZE_RESERVE_EXPIRED:
+    case TALER_EC_MERCHANT_PRIVATE_POST_TIP_AUTHORIZE_RESERVE_EXPIRED:
       http_status = MHD_HTTP_GONE;
       break;
-    case TALER_EC_TIP_AUTHORIZE_RESERVE_UNKNOWN:
+    case TALER_EC_MERCHANT_PRIVATE_POST_TIP_AUTHORIZE_RESERVE_UNKNOWN:
       http_status = MHD_HTTP_SERVICE_UNAVAILABLE;
       break;
-    case TALER_EC_TIP_AUTHORIZE_DB_RESERVE_NOT_FOUND:
+    case TALER_EC_MERCHANT_PRIVATE_POST_TIP_AUTHORIZE_RESERVE_NOT_FOUND:
       http_status = MHD_HTTP_NOT_FOUND;
       break;
     default:
@@ -166,7 +166,7 @@ TMH_private_post_reserves_ID_authorize_tip (const struct TMH_RequestHandler *rh,
     GNUNET_break_op (0);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       TALER_EC_RESERVES_INVALID_RESERVE_PUB,
+                                       TALER_EC_MERCHANT_GENERIC_RESERVE_PUB_MALFORMED,
                                        hc->infix);
   }
   return authorize_tip (rh,
diff --git a/src/backend/taler-merchant-httpd_private-post-reserves.c b/src/backend/taler-merchant-httpd_private-post-reserves.c
index ce50b24e..e2243936 100644
--- a/src/backend/taler-merchant-httpd_private-post-reserves.c
+++ b/src/backend/taler-merchant-httpd_private-post-reserves.c
@@ -192,22 +192,29 @@ handle_exchange (void *cls,
                                rc);
   if (NULL == hr)
   {
-    rc->ec = TALER_EC_TIMEOUT;
-    rc->http_status = MHD_HTTP_REQUEST_TIMEOUT;
+    rc->ec = TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT;
+    rc->http_status = MHD_HTTP_GATEWAY_TIMEOUT;
+    TMH_trigger_daemon ();   /* we resumed, kick MHD */
+    return;
+  }
+  if (NULL == eh)
+  {
+    rc->ec = TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE;
+    rc->http_status = MHD_HTTP_BAD_GATEWAY;
     TMH_trigger_daemon ();   /* we resumed, kick MHD */
     return;
   }
   keys = TALER_EXCHANGE_get_keys (eh);
   if (NULL == keys)
   {
-    rc->ec = TALER_EC_KEYS_INVALID;
-    rc->http_status = MHD_HTTP_FAILED_DEPENDENCY;
+    rc->ec = TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE;
+    rc->http_status = MHD_HTTP_BAD_GATEWAY;
     TMH_trigger_daemon ();   /* we resumed, kick MHD */
     return;
   }
   if (NULL == payto_uri)
   {
-    rc->ec = TALER_EC_RESERVES_POST_UNSUPPORTED_WIRE_METHOD;
+    rc->ec = TALER_EC_MERCHANT_PRIVATE_POST_RESERVES_UNSUPPORTED_WIRE_METHOD;
     rc->http_status = MHD_HTTP_CONFLICT;
     TMH_trigger_daemon ();   /* we resumed, kick MHD */
     return;
@@ -301,8 +308,8 @@ TMH_private_post_reserves (const struct TMH_RequestHandler *rh,
     if (qs < 0)
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_RESERVES_POST_DB_COMMIT_HARD_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_STORE_FAILED,
+                                         "reserve");
     return TALER_MHD_reply_json_pack (connection,
                                       MHD_HTTP_OK,
                                       "{s:o,s:s}",
diff --git a/src/backend/taler-merchant-httpd_private-post-transfers.c b/src/backend/taler-merchant-httpd_private-post-transfers.c
index 92e3be36..178c609c 100644
--- a/src/backend/taler-merchant-httpd_private-post-transfers.c
+++ b/src/backend/taler-merchant-httpd_private-post-transfers.c
@@ -31,9 +31,9 @@
 /**
  * How long to wait before giving up processing with the exchange?
  */
-#define TRANSFER_TIMEOUT (GNUNET_TIME_relative_multiply ( \
-                            GNUNET_TIME_UNIT_SECONDS, \
-                            30))
+#define TRANSFER_GENERIC_TIMEOUT (GNUNET_TIME_relative_multiply ( \
+                                    GNUNET_TIME_UNIT_SECONDS, \
+                                    30))
 
 /**
  * How often do we retry the simple INSERT database transaction?
@@ -306,10 +306,11 @@ check_transfer (void *cls,
           " s:I, s:o, s:o, s:o, s:o,"
           " s:o, s:o, s:o, s:o, s:o }",
           "code",
-          (json_int_t) TALER_EC_POST_TRANSFERS_CONFLICTING_REPORTS,
+          (json_int_t)
+          TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_CONFLICTING_REPORTS,
           "hint",
           TALER_ErrorCode_get_hint (
-            TALER_EC_POST_TRANSFERS_CONFLICTING_REPORTS),
+            TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_CONFLICTING_REPORTS),
           "exchange_url",
           exchange_url,
           "deposit_timestamp",
@@ -404,9 +405,11 @@ check_wire_fee (struct PostTransfersContext *ptc,
   ptc->response =
     TALER_MHD_make_json_pack (
       "{s:I, s:s, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:o}",
-      "code", (json_int_t) TALER_EC_POST_TRANSFERS_JSON_BAD_WIRE_FEE,
+      "code",
+      (json_int_t) TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_BAD_WIRE_FEE,
       "hint",
-      TALER_ErrorCode_get_hint (TALER_EC_POST_TRANSFERS_JSON_BAD_WIRE_FEE),
+      TALER_ErrorCode_get_hint (
+        TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_BAD_WIRE_FEE),
       "wire_fee", TALER_JSON_from_amount (wire_fee),
       "execution_time", GNUNET_JSON_from_time_abs (execution_time),
       "expected_wire_fee", TALER_JSON_from_amount (&expected_fee),
@@ -445,10 +448,11 @@ wire_transfer_cb (void *cls,
   {
     resume_transfer_with_response (
       ptc,
-      MHD_HTTP_FAILED_DEPENDENCY,
+      MHD_HTTP_BAD_GATEWAY,
       TALER_MHD_make_json_pack (
         "{s:I, s:I, s:I, s:O}",
-        "code", (json_int_t) TALER_EC_POST_TRANSFERS_EXCHANGE_ERROR,
+        "code",
+        (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_UNEXPECTED_STATUS,
         "exchange_code", (json_int_t) hr->ec,
         "exchange_http_status", (json_int_t) hr->http_status,
         "exchange_reply", hr->reply));
@@ -465,8 +469,8 @@ wire_transfer_cb (void *cls,
       GNUNET_break (0);
       resume_transfer_with_error (ptc,
                                   MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                  TALER_EC_POST_TRANSFERS_DB_STORE_TRANSFER_ERROR,
-                                  "could not start transaction");
+                                  TALER_EC_GENERIC_DB_START_FAILED,
+                                  NULL);
       return;
     }
     /* Ok, exchange answer is acceptable, store it */
@@ -488,8 +492,8 @@ retry:
       resume_transfer_with_error (
         ptc,
         MHD_HTTP_INTERNAL_SERVER_ERROR,
-        TALER_EC_POST_TRANSFERS_DB_STORE_TRANSFER_ERROR,
-        "failed to commit transaction to local database");
+        TALER_EC_GENERIC_DB_COMMIT_FAILED,
+        NULL);
       return;
     }
     if (0 <= qs)
@@ -503,8 +507,8 @@ retry:
     resume_transfer_with_error (
       ptc,
       MHD_HTTP_INTERNAL_SERVER_ERROR,
-      TALER_EC_POST_TRANSFERS_DB_STORE_TRANSFER_ERROR,
-      "repeated serialization failures trying to commit transaction to local database");
+      TALER_EC_GENERIC_DB_SOFT_FAILURE,
+      NULL);
     return;
   }
 
@@ -538,20 +542,33 @@ process_transfer_with_exchange (void *cls,
   (void) payto_uri;
   (void) exchange_trusted;
   ptc->fo = NULL;
-  if (MHD_HTTP_OK != hr->http_status)
+  if (NULL == hr)
+  {
+    resume_transfer_with_response (
+      ptc,
+      MHD_HTTP_GATEWAY_TIMEOUT,
+      TALER_MHD_make_json_pack (
+        "{s:s, s:I}"
+        "hint", TALER_ErrorCode_get_hint (
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT),
+        "code",
+        (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT));
+    return;
+  }
+  if (NULL == eh)
   {
     /* The request failed somehow */
     GNUNET_break_op (0);
     resume_transfer_with_response (
       ptc,
-      MHD_HTTP_FAILED_DEPENDENCY,
+      MHD_HTTP_BAD_GATEWAY,
       TALER_MHD_make_json_pack (
         (NULL != hr->reply)
         ? "{s:s, s:I, s:I, s:I, s:O}"
         : "{s:s, s:I, s:I, s:I}",
         "hint", TALER_ErrorCode_get_hint (
-          TALER_EC_POST_TRANSFERS_EXCHANGE_KEYS_FAILURE),
-        "code", (json_int_t) TALER_EC_POST_TRANSFERS_EXCHANGE_KEYS_FAILURE,
+          TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE),
+        "code", (json_int_t) TALER_EC_MERCHANT_GENERIC_EXCHANGE_CONNECT_FAILURE,
         "exchange_http_status", (json_int_t) hr->http_status,
         "exchange_code", (json_int_t) hr->ec,
         "exchange_reply", hr->reply));
@@ -567,9 +584,9 @@ process_transfer_with_exchange (void *cls,
     {
       GNUNET_break (0);
       resume_transfer_with_error (ptc,
-                                  MHD_HTTP_FAILED_DEPENDENCY,
-                                  TALER_EC_POST_TRANSFERS_EXCHANGE_KEYS_FAILURE,
-                                  "failed to get keys");
+                                  MHD_HTTP_BAD_GATEWAY,
+                                  TALER_EC_MERCHANT_GENERIC_EXCHANGE_KEYS_FAILURE,
+                                  NULL);
       return;
     }
     ptc->master_pub = keys->master_pub;
@@ -584,7 +601,7 @@ process_transfer_with_exchange (void *cls,
     GNUNET_break (0);
     resume_transfer_with_error (ptc,
                                 MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                TALER_EC_POST_TRANSFERS_REQUEST_ERROR,
+                                TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_REQUEST_ERROR,
                                 "failed to run GET /transfers/ on exchange");
   }
 }
@@ -631,8 +648,8 @@ verify_exchange_claim_cb (void *cls,
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     ptc->response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
     ptc->response
-      = TALER_MHD_make_error (TALER_EC_POST_TRANSFERS_DB_FETCH_DEPOSIT_ERROR,
-                              "failed to obtain deposit data from local database");
+      = TALER_MHD_make_error (TALER_EC_GENERIC_DB_FETCH_FAILED,
+                              "deposit by contract and coin");
     return;
   }
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
@@ -651,8 +668,8 @@ verify_exchange_claim_cb (void *cls,
     GNUNET_break (0);
     ptc->response_code = MHD_HTTP_INTERNAL_SERVER_ERROR;
     ptc->response =
-      TALER_MHD_make_error (TALER_EC_POST_TRANSFERS_DB_INTERNAL_LOGIC_ERROR,
-                            "internal logic error");
+      TALER_MHD_make_error (TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
+                            "check_transfer_result must not be NULL");
     return;
   }
   if (GNUNET_SYSERR == ptc->check_transfer_result)
@@ -807,9 +824,9 @@ handle_transfer_timeout (void *cls)
     ptc->wdh = NULL;
   }
   resume_transfer_with_error (ptc,
-                              MHD_HTTP_SERVICE_UNAVAILABLE,
-                              TALER_EC_POST_TRANSFERS_EXCHANGE_TIMEOUT,
-                              "exchange not reachable");
+                              MHD_HTTP_GATEWAY_TIMEOUT,
+                              TALER_EC_MERCHANT_GENERIC_EXCHANGE_TIMEOUT,
+                              NULL);
 }
 
 
@@ -926,8 +943,8 @@ queue:
       GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                         TALER_EC_POST_TRANSFERS_DB_LOOKUP_ERROR,
-                                         NULL);
+                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                         "transfer");
     }
     if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
       goto fetch;
@@ -981,8 +998,8 @@ queue:
         GNUNET_CONTAINER_multihashmap_destroy (map);
         return TALER_MHD_reply_with_error (connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                           TALER_EC_POST_TRANSFERS_DB_LOOKUP_ERROR,
-                                           NULL);
+                                           TALER_EC_GENERIC_DB_FETCH_FAILED,
+                                           "transfer summary");
       }
 
       deposit_sums = json_array ();
@@ -1020,8 +1037,8 @@ fetch:
     GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR == qs);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       TALER_EC_POST_TRANSFERS_DB_STORE_ERROR,
-                                       NULL);
+                                       TALER_EC_GENERIC_DB_STORE_FAILED,
+                                       "transfer");
   }
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
   {
@@ -1042,7 +1059,7 @@ fetch:
                   ptc->hc->instance->settings.id);
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         TALER_EC_POST_TRANSFERS_ACCOUNT_NOT_FOUND,
+                                         TALER_EC_MERCHANT_PRIVATE_POST_TRANSFERS_ACCOUNT_NOT_FOUND,
                                          ptc->payto_uri);
     }
   }
@@ -1059,7 +1076,7 @@ fetch:
                                          &process_transfer_with_exchange,
                                          ptc);
   ptc->timeout_task
-    = GNUNET_SCHEDULER_add_delayed (TRANSFER_TIMEOUT,
+    = GNUNET_SCHEDULER_add_delayed (TRANSFER_GENERIC_TIMEOUT,
                                     &handle_transfer_timeout,
                                     ptc);
   return MHD_YES;
diff --git a/src/backend/taler-merchant-httpd_statics.c b/src/backend/taler-merchant-httpd_statics.c
index 48d00ce4..ea94d9bf 100644
--- a/src/backend/taler-merchant-httpd_statics.c
+++ b/src/backend/taler-merchant-httpd_statics.c
@@ -125,7 +125,7 @@ TMH_return_static (const struct TMH_RequestHandler *rh,
                 hc->infix);
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       TALER_EC_ENDPOINT_UNKNOWN,
+                                       TALER_EC_GENERIC_ENDPOINT_UNKNOWN,
                                        hc->infix);
   }
 
diff --git a/src/backend/taler-merchant-httpd_templating.c b/src/backend/taler-merchant-httpd_templating.c
index b604f6ba..393104dc 100644
--- a/src/backend/taler-merchant-httpd_templating.c
+++ b/src/backend/taler-merchant-httpd_templating.c
@@ -146,7 +146,7 @@ TMH_return_from_template (struct MHD_Connection *connection,
       if (MHD_YES !=
           TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_NOT_ACCEPTABLE,
-                                      TALER_EC_MERCHANT_FAILED_TO_LOAD_TEMPLATE,
+                                      TALER_EC_MERCHANT_GENERIC_FAILED_TO_LOAD_TEMPLATE,
                                       template))
         return GNUNET_SYSERR;
       return GNUNET_NO;
@@ -164,7 +164,7 @@ TMH_return_from_template (struct MHD_Connection *connection,
       if (MHD_YES !=
           TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                      TALER_EC_MERCHANT_FAILED_TO_EXPAND_TEMPLATE,
+                                      TALER_EC_MERCHANT_GENERIC_FAILED_TO_EXPAND_TEMPLATE,
                                       template))
         return GNUNET_SYSERR;
       return GNUNET_NO;