“showposts” not working in WP_Query

I upgraded my WordPress blog from 2.5.1 to 2.6 and noticed that this piece of code will work:

<?php $my_query = new WP_Query('category_name=home&showposts=-1'); ?>

<?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
  <?php echo ", $post->post_name"; ?>
<?php endwhile; ?>

And this one won’t:

<?php $my_query = new WP_Query('category_name=home&showposts=3'); ?>

<?php while ($my_query->have_posts()) : $my_query->the_post(); ?>
  <?php echo ", $post->post_name"; ?>
<?php endwhile; ?>

The difference between these is in the query. When I put -1 for showposts, it works. If I put any other number (ie. 3), the output disappears completely.

What happened?