Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.174.2.15
diff -u -p -r1.174.2.15 form.inc
--- includes/form.inc	15 Sep 2008 06:03:17 -0000	1.174.2.15
+++ includes/form.inc	2 Nov 2008 00:32:42 -0000
@@ -1038,8 +1038,8 @@ function theme_fieldset($element) {
     }
 
     $element['#attributes']['class'] .= ' collapsible';
-    if ($element['#collapsed']) {
-     $element['#attributes']['class'] .= ' collapsed';
+    if (!empty($element['#collapsed'])) {
+      $element['#attributes']['class'] .= ' collapsed';
     }
   }