Disable HTML escaping for rendering HTML in label for KnpMenu in KnpMenuBundle in Symfony2 (used to embed Twitter Bootstrap Glyphicons)

Builder.php

<?php

// Menu builder class
public function topUserMenu(Request $request)
{
  $user = $this->securityContext->getToken()->getUser();
  $menu = $this->factory->createItem('root');
  $userDrop = $menu->addChild(
    '<i class="icon-user icon-white"></i> ' . $user->getFirstname() . ' ' . $user->getLastname(),
    array('extras' => array('safe_label' => true))
  );
  $userDrop->addChild('<i class="icon-off"></i> Logout', array('uri' => $this->router->generate('logout'), 'extras' => array('safe_label' => true)));
  return $menu;
}

layout.html.twig

{{ knp_menu_render('topUserMenu', {'nav_type': 'navbar', 'pull': 'right', 'allow_safe_labels': true}) }}