diff -r ed590800fde7 Modules/fcntlmodule.c
--- a/Modules/fcntlmodule.c	Sun Sep 15 10:37:57 2013 +0200
+++ b/Modules/fcntlmodule.c	Sun Sep 15 17:06:00 2013 +0800
@@ -626,6 +626,8 @@
         return NULL;
 
     /* Add some symbolic constants to the module */
-    all_ins(m);
+    if (all_ins(m) < 0)
+        return NULL;
+
     return m;
 }