diff --git a/lib/action.php b/lib/action.php
index dd84977f0d..3efb65a65e 100644
--- a/lib/action.php
+++ b/lib/action.php
@@ -287,7 +287,7 @@ class Action extends HTMLOutputter // lawsuit
 
     function showCore()
     {
-        $this->elementStart('div', array('class' => 'core'));
+        $this->elementStart('div', array('id' => 'core'));
         $this->showLocalNav();
         $this->showContentBlock();
         $this->showAside();