Problem with menu

I’m trying to generate a menu in my template using the following code:

<?php
wp_nav_menu(array(
    'theme_location' => 'main-menu',
    'container' => 'nav',
    'container_id' => 'menu',
    'menu_class' => 'navigation',
    'menu_id' => 'nav'
));
?>

What I should be ending up with is this:

<nav id="menu">
    <ul class="navigation" id="nav">
	<li><a href="http://localhost/sample-page/">Sample Page</a></li>
    </ul>
</nav>

Instead I get this:

<div class="navigation">
    <ul>
        <li class="page_item page-item-2"><a href="http://localhost/sample-page/">Sample Page</a></li>
    </ul>
</div>

Am I doing something wrong?