WordPress get_posts attachments orderby

I am using this to get a list of all attachments of a post in WordPress 3.2

 $args = array(
      'numberposts' => -1,
      'post_status' => 'any',
      'post_type' => 'attachment',
      'orderby' => 'title',
      'order' => 'ASC'
 );

 get_posts($args);

Nothing I do in the ‘orderby’ argument has any effect on the order in which the attachments are displayed. Can you order attachments by title? alphabetical order? in WordPress