diff --git a/toolkit/mozapps/extensions/content/extensions.js b/toolkit/mozapps/extensions/content/extensions.js
index 19fe4f1d9559..cc109e768aae 100644
--- a/toolkit/mozapps/extensions/content/extensions.js
+++ b/toolkit/mozapps/extensions/content/extensions.js
@@ -988,7 +988,7 @@ var gExtensionsViewController = {
         try {
           var prefs = Components.classes["@mozilla.org/preferences-service;1"]
                                  .getService(Components.interfaces.nsIPrefBranch);
-          instantApply = prefs.getBoolPref("browser.preferences.instantApply");
+          var instantApply = prefs.getBoolPref("browser.preferences.instantApply");
           features = "chrome,titlebar,toolbar,centerscreen" + (instantApply ? ",dialog=no" : ",modal");
         }
         catch (e) {