diff --git a/lib/outputrequirementslib.php b/lib/outputrequirementslib.php
index 24a3f566d1f..b58dbe2af4d 100644
--- a/lib/outputrequirementslib.php
+++ b/lib/outputrequirementslib.php
@@ -240,6 +240,7 @@ class page_requirements_manager {
             $this->YUI_config->debug = true;
         } else {
             $this->yui3loader->filter = null;
+            $this->YUI_config->groups['moodle']['filter'] = null;
             $this->YUI_config->debug = false;
         }