Rewrite rule not seen by WP?

I addded the following code to my functions.php file:

function add_rewrite_menus(){
 add_rewrite_rule('^property-detail/(.+)/$','/property-detail/?property_id=$matches[1]','top');
 add_rewrite_tag('%property_id%','([^&]+)');
}
add_action('init', 'add_rewrite_menus');

But the rewrite rule never shows up in my rules. Any ideas why?