includes/form.inc |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/includes/form.inc b/includes/form.inc
index c0163ca..d6b6523 100644
--- a/includes/form.inc
+++ b/includes/form.inc
@@ -3973,7 +3973,8 @@ function _form_set_class(&$element, $class = array()) {
   if (!empty($element['#required'])) {
     $element['#attributes']['class'][] = 'required';
   }
-  if (isset($element['#parents']) && form_get_error($element)) {
+  $form_error = form_get_error($element);
+  if (isset($element['#parents']) && isset($form_error)) {
     $element['#attributes']['class'][] = 'error';
   }
 }