diff --git a/PHPCI/Helper/Lang.php b/PHPCI/Helper/Lang.php
index 3771db86..42027cee 100644
--- a/PHPCI/Helper/Lang.php
+++ b/PHPCI/Helper/Lang.php
@@ -37,7 +37,7 @@ class Lang
             return call_user_func_array('sprintf', $vars);
         }
 
-        return $string;
+        return '%%MISSING STRING: ' . $string . '%%';
     }
 
     /**