--- a/mobile/chrome/content/browser-ui.js
+++ b/mobile/chrome/content/browser-ui.js
@@ -920,17 +920,17 @@ var BrowserUI = {
       case "cmd_lockscreen":
       {
         let locked = gPrefService.getBoolPref("toolkit.screen.lock");
         gPrefService.setBoolPref("toolkit.screen.lock", !locked);
 
         let strings = Elements.browserBundle;
         let alerts = Cc["@mozilla.org/alerts-service;1"].getService(Ci.nsIAlertsService);
         alerts.showAlertNotification(null, strings.getString("alertLockScreen"),
-                                     strings.getString("alertLockScreen." + (locked ? "locked" : "unlocked")), false, "", null);
+                                     strings.getString("alertLockScreen." + (!locked ? "locked" : "unlocked")), false, "", null);
         break;
       }
     }
   }
 };
 
 var PageActions = {
   get _permissionManager() {