diff --git a/hierarchical_select.module b/hierarchical_select.module
index b9ace69..286ed0d 100644
--- a/hierarchical_select.module
+++ b/hierarchical_select.module
@@ -874,7 +874,8 @@ function _hierarchical_select_validate(&$element, &$form_state) {
 
   // We have to check again for errors. This line is taken litterally from
   // form.inc, so it works in an identical way.
-  if ($element['#required'] && (!count($element['#value']) || (is_string($element['#value']) && strlen(trim($element['#value'])) == 0))) {
+  // We only check in a real submission rather than an ajax update.
+  if ($element['#required'] && $form_state['submit_handlers'][0] !== 'hierarchical_select_ajax_update_submit' && (!count($element['#value']) || (is_string($element['#value']) && strlen(trim($element['#value'])) == 0))) {
     form_error($element, t('!name field is required.', array('!name' => $element['#title'])));
     _hierarchical_select_form_set_error_class($element);
   }