diff --git a/admin/tool/templatelibrary/classes/external.php b/admin/tool/templatelibrary/classes/external.php
index 488fb3c5409..b92f60859e7 100644
--- a/admin/tool/templatelibrary/classes/external.php
+++ b/admin/tool/templatelibrary/classes/external.php
@@ -73,9 +73,10 @@ class external extends external_api {
      * Loads the list of templates.
      * @param string $component Limit the search to a component.
      * @param string $search The search string.
+     * @param string $themename The name of theme
      * @return array[string]
      */
-    public static function list_templates($component, $search, $themename) {
+    public static function list_templates($component, $search, $themename = '') {
         $params = self::validate_parameters(self::list_templates_parameters(),
                                             array(
                                                 'component' => $component,