diff --git a/js/src/Makefile.ref b/js/src/Makefile.ref
index e5b2af0fc8dd..c214ed6d139b 100644
--- a/js/src/Makefile.ref
+++ b/js/src/Makefile.ref
@@ -1,3 +1,4 @@
+# -*- Mode: makefile -*-
 #
 # The contents of this file are subject to the Netscape Public
 # License Version 1.1 (the "License"); you may not use this file