Additional category in category page loop

I’m using this code in category.php:

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
global $wp_query;
query_posts(
	array_merge(array(
      'paged' => $paged,
      'posts_per_page' => 8),
	$wp_query->query
	)
);

But I’d like to show another category on that same page, so I tried:

query_posts(
	array_merge(array(
      category__in => array(25,26),
      'paged' => $paged,
      'posts_per_page' => 8),
	$wp_query->query
	)
);

but that didn’t work.

How do I show posts from category 25 and 26 in the category page of category 25?

Thanks!