--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1854,17 +1854,17 @@ BrowserGlue.prototype = {
       let animate = Services.prefs.getBoolPref("browser.tabs.animate", true) &&
                     Services.prefs.getBoolPref("browser.fullscreen.animate", true) &&
                     !Services.prefs.getBoolPref("alerts.disableSlidingEffect", false);
 
       Services.prefs.setBoolPref("toolkit.cosmeticAnimations.enabled", animate);
 
       Services.prefs.clearUserPref("browser.tabs.animate");
       Services.prefs.clearUserPref("browser.fullscreen.animate");
-      Services.prefs.clearUserPref("browser.tabs.animate");
+      Services.prefs.clearUserPref("alerts.disableSlidingEffect");
     }
 
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },
 
   // ------------------------------
   // public nsIBrowserGlue members