diff --git a/lib/server/socket.js b/lib/server/socket.js
index 32ba8a21..e5faa345 100644
--- a/lib/server/socket.js
+++ b/lib/server/socket.js
@@ -55,7 +55,7 @@
              * https://github.com/LearnBoost/socket.io/issues/1314
              *
              */
-            if (!Win32) {
+            if (!WIN32) {
                 lListen.set('browser client minification', true);
                 lListen.set('browser client gzip', true);
             }