wordpress wp_nav_menu add span at the end of ul

Question

I am using wordpress and wp_nav_menu function to get navigation, and I want to add a span inside ul like this:

<ul>
  <li><a href="">url1</a></li>
  <li><a href="">url2</a></li>
  <li><a href="">url3</a></li>
  <span></span> <-- I want to add this
</ul>

I googled a few times but can't find out what options I have to change in wp_nav_menu

<?php wp_nav_menu( array( 
    'theme_location'  => 'primary',
    'menu'            => '',
    'container'       => 'div',
    'container_class' => '',
    'container_id'    => '',
    'menu_class'      => 'menu',
    'menu_id'         => '',
    'echo'            => true,
    'fallback_cb'     => 'wp_page_menu',
    'before'          => '',
    'after'           => '',
    'link_before'     => '',
    'link_after'      => '',
    'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
    'depth'           => 0,
    'walker'          => ''
    ) ); ?>

Answer 1

http://codex.wordpress.org/Function_Reference/wp_nav_menu

Look example with $items_wrap