adding support for Custom menu(introduced in 3.0) to older theme

Okay so I followed each step as in http://codex.wordpress.org/Navigation_Menus

Registered the menu in theme as ‘primary’ in functions.php

<?php

function register_my_menus() {
  register_nav_menus(
    array('header-menu' => __( 'primary' ) )
  );
}

add_action( 'init', 'register_my_menus' );

and added the following code at the header.php where I want my custom menu to be displayed

<?php wp_nav_menu( array( 'theme_location' => 'primary', 'container' => '' ) ); ?>

However I am unable to output the custom menu items , seems like it displaying out menu in new div id , which is not required and is supposed to disabled using the ‘container’=> ” but still ads a div code ?