diff --git a/lib/x11/auth.js b/lib/x11/auth.js
index 19d2fe4..1186358 100644
--- a/lib/x11/auth.js
+++ b/lib/x11/auth.js
@@ -80,7 +80,7 @@ module.exports = function( display, host, cb )
         }
 
         var auth = parseXauth(data);
-        for (cookieNum in auth)
+        for (var cookieNum in auth)
         {
             var cookie = auth[cookieNum];
             if (cookie.display == display && cookie.address == host)