diff --git a/xm.js b/xm.js
index 73adf5c..c55ac4f 100644
--- a/xm.js
+++ b/xm.js
@@ -1271,4 +1271,4 @@ window.onload = function() {
   }
   DownloadXM(uri);
 }
-})(window, document);
+})(window || {}, document);