Query pages based on tags

On a site that I’m working on I’ve added the ability to tag pages. These tags should then be used in a query to retrieve all associated pages of a tag.

In my functions file –

// Add tag support to Pages
function tags_support_all() {
    register_taxonomy_for_object_type('post_tag', 'page');
}
function tags_support_query($wp_query) {
    if ($wp_query->get('tag')) $wp_query->set('post_type', 'any');
}
add_action('init', 'tags_support_all');
add_action('pre_get_posts', 'tags_support_query');

Query –

$tag = get_query_var('tag');
$articles = new WP_Query( array(
    'showposts' => -1,
    'tag' => $tag,
    'meta_key' => 'date',
    'orderby' => 'meta_value_num',
    'order' => 'DESC'
    )
);

For some reason it doesn’t match my pages agains the tags. I can see that the tags are being added under my tags collection in the admin panel, but supposedly there’s a setting missing that makes WP only look for matching posts.

To answer birgie’s question, I get this result when using printf –

SELECT   wp_posts.* FROM wp_posts  INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) WHERE 1=1  AND ( wp_term_relationships.term_taxonomy_id IN (5) ) AND wp_posts.post_type IN ('post', 'page', 'attachment') AND (wp_posts.post_status = 'publish') AND (wp_postmeta.meta_key = 'date' ) GROUP BY wp_posts.ID ORDER BY wp_postmeta.meta_value+0 DESC