--- a/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
+++ b/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
@@ -1,18 +1,19 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 const { classes: Cc, interfaces: Ci, results: Cr } = Components;
 
 var dbService = Cc["@mozilla.org/url-classifier/dbservice;1"]
                 .getService(Ci.nsIUrlClassifierDBService);
 
+var timer;
 function setTimeout(callback, delay) {
-  let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   timer.initWithCallback({ notify: callback },
                            delay,
                            Ci.nsITimer.TYPE_ONE_SHOT);
 }
 
 function doUpdate(update) {
   let listener = {
     QueryInterface: function(iid)