diff --git a/field_group.module b/field_group.module
index b2711b2..995e19e 100644
--- a/field_group.module
+++ b/field_group.module
@@ -315,7 +315,11 @@ function field_group_form_process(array &$element, FormStateInterface $form_stat
       }
 
       $group_parents = $element['#array_parents'];
-      $group_parents[] = empty($group->parent_name) ? $group->region : $group->parent_name;
+      $region = 'content';
+      if (isset($group->region)) {
+        $region = $group->region;
+      }
+      $group_parents[] = empty($group->parent_name) ? $region : $group->parent_name;
       $group_references[$group_name] = &$element[$group_name];
       $element[$group_name]['#group'] = implode('][', $group_parents);