Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.327
diff -u -p -r1.327 form.inc
--- includes/form.inc	11 Apr 2009 22:19:44 -0000	1.327
+++ includes/form.inc	18 Apr 2009 20:22:53 -0000
@@ -2670,7 +2670,7 @@ function _form_set_class(&$element, $cla
   if ($element['#required']) {
     $class[] = 'required';
   }
-  if (form_get_error($element)) {
+  if (form_get_error($element) !== NULL) {
     $class[] = 'error';
   }
   if (isset($element['#attributes']['class'])) {