Index: system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.633
diff -u -r1.633 system.module
--- system.module	26 Oct 2008 18:06:39 -0000	1.633
+++ system.module	27 Oct 2008 06:30:40 -0000
@@ -1339,7 +1339,7 @@
   // Confirm form fails duplication check, as the form values rarely change -- so skip it.
   $form['#skip_duplicate_check'] = TRUE;
 
-  $form['#attributes'] = array('class' => 'confirmation');
+  $form['#attributes']['class'] .= ' confirmation';
   $form['description'] = array('#markup' => $description);
   $form[$name] = array('#type' => 'hidden', '#value' => 1);