Page navi using query_posts

Hello!

I created a layout for a special category. There, I limited the number of posts in the page:

<?php query_posts('cat=4&posts_per_page=12'); ?>

The problem is I can’t navigate to old posts… The code of I put is that:

<p id="navega"><?php next_posts_link('Back') ?> . <?php previous_posts_link('Next') ?></p>

But doesn’t work… When I click in the link, the URL change to https://myurl.com/category/cat4/page/2/, but the posts as the same…

What I’m doing wrong?

Best regards!