diff --git a/modules/user/user.module b/modules/user/user.module
index 33c81f6fe2c0edd179173499b8ff69c380e6acb7..34d737789d52ff9c54f4bb9b4063686c5061d832 100644
--- a/modules/user/user.module
+++ b/modules/user/user.module
@@ -482,7 +482,7 @@ function user_access($string, $account = NULL, $reset = FALSE) {
   static $perm = array();
 
   if ($reset) {
-    unset($perm);
+    $perm = array();
   }
 
   if (is_null($account)) {