diff --git a/action.php b/action.php
index 2b008b5..a1b5b21 100644
--- a/action.php
+++ b/action.php
@@ -30,7 +30,7 @@ function getInfo() {
     /**
      * Register its handlers with the DokuWiki's event controller
      */
-    function register(&$controller) {
+    function register(Doku_Event_Handler $controller) {
         $controller->register_hook('TPL_METAHEADER_OUTPUT', 'BEFORE', $this, 'tableplot_hookjs');
     }
 
diff --git a/syntax.php b/syntax.php
index 61f871e..55ad794 100644
--- a/syntax.php
+++ b/syntax.php
@@ -56,7 +56,7 @@ function connectTo($mode) {
     /**
      * Handle the match
      */
-    function handle($match, $state, $pos, &$handler){
+    function handle($match, $state, $pos, Doku_Handler $handler){
         parse_str($match, $return);   
         return $return;
     }
@@ -68,7 +68,7 @@ function handle($match, $state, $pos, &$handler){
  * @author   Tom Cafferty <tcafferty@glocalfocal.com>
  *
  */
-    function render($mode, &$renderer, $data) {
+    function render($mode, Doku_Renderer $renderer, $data) {
       global $INFO;
       global $ID;
       global $conf;