diff --git a/toolkit/mozapps/extensions/test/browser/browser_bug557956.js b/toolkit/mozapps/extensions/test/browser/browser_bug557956.js
index c0ea1a90338b..033ea5cb89fd 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_bug557956.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_bug557956.js
@@ -30,8 +30,6 @@ function test() {
 }
 
 function end_test() {
-  Services.prefs.clearUserPref("extensions.update.url");
-
   // Test generates a lot of available installs so just cancel them all
   AddonManager.getAllInstalls(function(aInstalls) {
     aInstalls.forEach(function(aInstall) {
@@ -46,7 +44,7 @@ function install_test_addons(aCallback) {
   var installs = [];
 
   // Use a blank update URL
-  Services.prefs.setCharPref("extensions.update.url", TESTROOT + "missing.rdf");
+  Services.prefs.setCharPref(PREF_UPDATEURL, TESTROOT + "missing.rdf");
 
   ["browser_bug557956_1",
    "browser_bug557956_2",
@@ -69,7 +67,7 @@ function install_test_addons(aCallback) {
       this.installCount++;
       if (this.installCount == installs.length) {
         // Switch to the test update URL
-        Services.prefs.setCharPref("extensions.update.url", TESTROOT + "browser_bug557956.rdf");
+        Services.prefs.setCharPref(PREF_UPDATEURL, TESTROOT + "browser_bug557956.rdf");
 
         aCallback();
       }
diff --git a/toolkit/mozapps/extensions/test/browser/head.js b/toolkit/mozapps/extensions/test/browser/head.js
index 6bddd0cf3f33..d4c1d51bdde0 100644
--- a/toolkit/mozapps/extensions/test/browser/head.js
+++ b/toolkit/mozapps/extensions/test/browser/head.js
@@ -20,6 +20,7 @@ const TESTROOT = "http://example.com/" + RELATIVE_DIR;
 const TESTROOT2 = "http://example.org/" + RELATIVE_DIR;
 const CHROMEROOT = pathParts.join("/") + "/";
 const PREF_DISCOVERURL = "extensions.webservice.discoverURL";
+const PREF_UPDATEURL = "extensions.update.url";
 
 const MANAGER_URI = "about:addons";
 const INSTALL_URI = "chrome://mozapps/content/xpinstall/xpinstallConfirm.xul";
@@ -33,6 +34,7 @@ var gTestStart = null;
 var gUseInContentUI = !gTestInWindow && ("switchToTabHavingURI" in window);
 
 var gDiscoveryURL = Services.prefs.getCharPref(PREF_DISCOVERURL);
+var gUpdateURL = Services.prefs.getCharPref(PREF_UPDATEURL);
 
 // Turn logging on for all tests
 Services.prefs.setBoolPref(PREF_LOGGING_ENABLED, true);
@@ -47,6 +49,7 @@ registerCleanupFunction(function() {
   }
 
   Services.prefs.setCharPref(PREF_DISCOVERURL, gDiscoveryURL);
+  Services.prefs.setCharPref(PREF_UPDATEURL, gUpdateURL);
 
   // Throw an error if the add-ons manager window is open anywhere
   var windows = Services.wm.getEnumerator("Addons:Manager");