Problem with conditional posts navigation

I’ve searched the forums and almost have this figured out, but there’s still a problem.

To prevent empty tags, I’m using a conditional statement to show or hide the navigation to older/newer posts. The code I’m using in my theme is:

<?php if (show_posts_nav()) : ?>
<ul class="pagination">
<li class="prevlink"><?php next_posts_link('Older Posts'); ?></li>
<li class="nextlink"><?php previous_posts_link('Newer Posts'); ?></li>
</ul>
<?php endif; ?>

and in my functions I have:

function show_posts_nav() {
	global $wp_query;
	return ($wp_query->max_num_pages > 1);
}

If there’s no navigation necessary, there’s no ul. But if there’s only one link necessary, I still get an empty li tag.

Anyone know how to prevent that?