diff --git a/action.php b/action.php
index 99a30cd..f082f9d 100644
--- a/action.php
+++ b/action.php
@@ -19,7 +19,7 @@ class action_plugin_plantuml extends DokuWiki_Action_Plugin {
     /**
      * Register the event handler
      */
-    function register(&$controller) {
+    function register(Doku_Event_Handler $controller) {
       if($this->getConf('button_enabled') == '1')
         $controller->register_hook('TOOLBAR_DEFINE', 'AFTER', $this, 'insert_button', array ());
     }
diff --git a/syntax.php b/syntax.php
index ef1aef9..fc45a90 100644
--- a/syntax.php
+++ b/syntax.php
@@ -38,7 +38,7 @@ function connectTo($mode) {
     /**
      * Handle the match
      */
-    function handle($match, $state, $pos, &$handler) {
+    function handle($match, $state, $pos, Doku_Handler $handler) {
         // echo "handle: state=$state<br>";
         // echo "handle: match=$match<br>";
         // echo "handle: pos=$pos<br>";
@@ -109,7 +109,7 @@ function _cachename($data, $ext){
     /**
      * Create output
      */
-    function render($mode, &$renderer, $data) {
+    function render($mode, Doku_Renderer $renderer, $data) {
         if ($mode == 'xhtml') {
             $img = DOKU_BASE . 'lib/plugins/plantuml/img.php?' . buildURLParams($data);