diff --git a/phpBB/includes/session.php b/phpBB/includes/session.php
index 3e315c5db8..60e28f490e 100644
--- a/phpBB/includes/session.php
+++ b/phpBB/includes/session.php
@@ -531,7 +531,7 @@ class auth
 			$db->sql_freeresult($result);
 
 			$cache->put('acl_options', $this->acl_options);
-			$auth->acl_clear_prefetch();
+			$this->acl_clear_prefetch();
 			$this->acl_cache($userdata);
 		}
 		else if (trim($userdata['user_permissions']) == '')