query_posts function not working in 2011 theme

hey, wondering if I’m doing something wrong. I’m trying to alter the default query of index.php in the 2011 theme with query_posts:

get_header(); ?>

		<div id="primary">
			<div id="content" role="main">

			<?php if ( have_posts() ) : ?>
    <?php 

query_posts( 'posts_per_page=1');//just to get a visible result.

?>
				<?php twentyeleven_content_nav( 'nav-above' ); ?>

				<?php /* Start the Loop */ ?>
				<?php while ( have_posts() ) : the_post(); ?>

but for some reason it still keeps showing the default, 20 or whatever it is posts.. Any idea why this could be? (tried with the query posts above the start of the conditional as well, but same.)