XSPF putting blank links into main navigation menu for *every* node

With XSPF module enabled, I get two blank links in my navigation menu for "node/nid/xspf". Is there something to blame in this function below?

/**
 * Implementation of hook_menu().
 */
function xspf_playlist_node_menu($may_cache) {
  $items = array();
  if ($may_cache) {
    // this is the legacy path
    $items[] = array(
      'path' => 'xspf/node',
      'callback' => 'xspf_playlist_node_view',
      'access' => user_access('access content'),
    );
  }
  // new node-centric path
  $items[] = array(
    'path' => 'node/'. arg(1) .'/xspf',
    'callback' => 'xspf_playlist_node_view',
    'callback arguments' => array(arg(1)),
    'access' => user_access('access content'),
  );
  return $items;
}