diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index c828037..5556f38 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -2438,7 +2438,8 @@ function drupal_valid_test_ua() {
     }
   }
 
-  return FALSE;
+  $test_prefix = FALSE;
+  return $test_prefix;
 }
 
 /**