Wordpress custom taxonomies

I have created a custom taxonomies

function create_my_taxonomies() {
    register_taxonomy('featured', 'post', array(
          'hierarchical' => false, 'label' => 'Featured',
          'query_var' => true, 'rewrite' => true));

Then I try to get the posts that have only a tag of that custom taxonomies

query_posts( array( 'featured' => 'gallery', 'showposts' => 10 ) );

The problem is that I get all the posts. I don’t have another loop before, so is the first use of the wp_query object