diff --git a/lib/plugins/authad/action.php b/lib/plugins/authad/action.php
index 97be9897e676303a238097aa879c33118714c3ff..bc0f90c7ed3121bc974380d8aef2b360745bad0b 100644
--- a/lib/plugins/authad/action.php
+++ b/lib/plugins/authad/action.php
@@ -17,7 +17,7 @@ class action_plugin_authad extends DokuWiki_Action_Plugin {
     /**
      * Registers a callback function for a given event
      */
-    public function register(Doku_Event_Handler &$controller) {
+    public function register(Doku_Event_Handler $controller) {
 
         $controller->register_hook('AUTH_LOGIN_CHECK', 'BEFORE', $this, 'handle_auth_login_check');
         $controller->register_hook('HTML_LOGINFORM_OUTPUT', 'BEFORE', $this, 'handle_html_loginform_output');