diff --git a/CSSEditorPlugin.php b/CSSEditorPlugin.php
index b845020..2015653 100644
--- a/CSSEditorPlugin.php
+++ b/CSSEditorPlugin.php
@@ -41,6 +41,7 @@ public function hookConfig($args)
         $config->set('CSS.Trusted', TRUE);
         $config->set('HTML.DefinitionID', 'html5-definitions'); // unqiue id
         $config->set('HTML.DefinitionRev', 1);
+        $config->set('Cache.DefinitionImpl', null);
 
         if ($def = $config->maybeGetRawHTMLDefinition())
         {