We're using URLMapper, not Net_URL_Mapper

plugins/Directory/DirectoryPlugin.php

@@ -71,12 +71,12 @@ class DirectoryPlugin extends Plugin
     /**
      * Map URLs to actions
      *
-     * @param Net_URL_Mapper $m path-to-action mapper
+     * @param URLMapper $m path-to-action mapper
      *
      * @return boolean hook value; true means continue processing,
      *         false means stop.
      */
-    function onRouterInitialized($m)
+    public function onRouterInitialized(URLMapper $m)
     {
 
         $m->connect(