--- form.inc	2015-12-24 16:28:18.073595977 +0530
+++ text.inc	2015-12-24 16:25:28.445603071 +0530
@@ -1340,7 +1340,7 @@
   $t = get_t();
 
   // Recurse through all children.
-  foreach (element_children($elements) as $key) {
+  foreach (element_children($elements, TRUE) as $key) {
     if (isset($elements[$key]) && $elements[$key]) {
       _form_validate($elements[$key], $form_state);
     }