Menu tree structure fails to build

If you create a tree structure of MENU_NORMAL_ITEMs via hook_menu only the parent element (root element) will be shown. I attached a patch to solve this issue in include/menu.inc. Use this code to reproduce the issue:

function YOUR_MODULE_menu($may_cache) {
  $items = array();
  if ($may_cache) {
  }
  else {
    $items[] = array(
      'path' => 'parent',
      'title' => 'Parent',
      'access' => TRUE,
      'type' => MENU_NORMAL_ITEM | MENU_EXPANDED,
    );
    $items[] = array(
      'path' => 'parent/child',
      'title' => 'Child',
      'access' => TRUE,
      'type' => MENU_NORMAL_ITEM,
    );
  }
  return $items;
}