diff --git a/core/modules/field_ui/field_ui.admin.inc b/core/modules/field_ui/field_ui.admin.inc
index 45b4fc5..c4b80c1 100644
--- a/core/modules/field_ui/field_ui.admin.inc
+++ b/core/modules/field_ui/field_ui.admin.inc
@@ -1066,7 +1066,7 @@ function field_ui_field_edit_form_validate($form, &$form_state) {
   $cardinality_other = &$form_state['values']['field']['cardinality_other'];
   if ($cardinality == 'other') {
     if (empty($cardinality_other)) {
-      form_error($form['field']['cardinality_other'], t('Number of values is required.'));
+      form_error($form['field']['cardinality']['cardinality_other'], t('Number of values is required.'));
     }
     else {
       $cardinality = $cardinality_other;