[Plugin: Access Keys for WP Navigation Menus] Not working

Hi, I have activated the plugin and acceskey settings for each navigation. The navigation code prints without the acceskey. It does not work.

The code i get:

<ul class="menu" id="nav">
  <li class="menu-item menu-item-type-custom current-menu-item current_page_item menu-item-home menu-item-4" id="menu-item-4"><a href="http://localhost/jhr/">Blog</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-8" id="menu-item-8"><a href="http://localhost/jhr/?page_id=6">Tags</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-5" id="menu-item-5"><a href="http://localhost/jhr/?page_id=2">Sobre mí</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-13" id="menu-item-13"><a href="http://localhost/jhr/?page_id=11">Contacto</a></li>
</ul>

and the code I want

<ul class="menu" id="nav">
  <li class="menu-item menu-item-type-custom current-menu-item current_page_item menu-item-home menu-item-4" id="menu-item-4"><a href="http://localhost/jhr/" accesskey="b">Blog</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-8" id="menu-item-8"><a href="http://localhost/jhr/?page_id=6" accesskey="t">Tags</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-5" id="menu-item-5"><a href="http://localhost/jhr/?page_id=2" accesskey="s">Sobre mí</a></li>
  <li class="menu-item menu-item-type-post_type menu-item-13" id="menu-item-13"><a href="http://localhost/jhr/?page_id=11" accesskey="c">Contacto</a></li>
</ul>

http://wordpress.org/extend/plugins/wordpress-nav-menus-access-keys/