1 files changed, 4 insertions, 4 deletions
diff --git a/lib/_http_incoming.js b/lib/_http_incoming.js
index f11d098031..f609e4fc21 100644
--- a/lib/_http_incoming.js
+++ b/lib/_http_incoming.js
@@ -125,7 +125,7 @@ IncomingMessage.prototype._addHeaderLine = function(field, value) {
   switch (field) {
     // Array headers:
     case 'set-cookie':
-      if (!IS_UNDEFINED(dest[field])) {
+      if (!util.isUndefined(dest[field])) {
         dest[field].push(value);
       } else {
         dest[field] = [value];
@@ -145,7 +145,7 @@ IncomingMessage.prototype._addHeaderLine = function(field, value) {
     case 'proxy-authenticate':
     case 'sec-websocket-extensions':
     case 'sec-websocket-protocol':
-      if (!IS_UNDEFINED(dest[field])) {
+      if (!util.isUndefined(dest[field])) {
         dest[field] += ', ' + value;
       } else {
         dest[field] = value;
@@ -156,14 +156,14 @@ IncomingMessage.prototype._addHeaderLine = function(field, value) {
     default:
       if (field.slice(0, 2) == 'x-') {
         // except for x-
-        if (!IS_UNDEFINED(dest[field])) {
+        if (!util.isUndefined(dest[field])) {
           dest[field] += ', ' + value;
         } else {
           dest[field] = value;
         }
       } else {
         // drop duplicates
-        if (IS_UNDEFINED(dest[field])) dest[field] = value;
+        if (util.isUndefined(dest[field])) dest[field] = value;
       }
       break;
   }