Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.437
diff -u -r1.437 theme.inc
--- includes/theme.inc	20 Sep 2008 20:22:23 -0000	1.437
+++ includes/theme.inc	11 Oct 2008 01:08:53 -0000
@@ -1122,6 +1122,10 @@
       if (isset($link['href']) && ($link['href'] == $_GET['q'] || ($link['href'] == '<front>' && drupal_is_front_page()))) {
         $class .= ' active';
       }
+      // Add active-trail class to <li> if enclosed <a> link has it.
+      if (isset($link['attributes']['class']) && stristr($link['attributes']['class'], 'active-trail') == TRUE) {
+        $class .= ' active-trail';
+      }
       $output .= '<li' . drupal_attributes(array('class' => $class)) . '>';
 
       if (isset($link['href'])) {