zii.widgets.CMenu setting an option to highlight

I have an admin module, and the menu in the main layout is defined like this:

array('label'=>'Admin', 'url'=>array('/admin')),

But when they click the link and arrive to /admin, the Admin option of the menu is not highlighted.

I have to direct users to ‘/admin/default/index’ for the option to highlight, but then the URL doesn’t look so pretty.

How can I tell the CMenu to highlight the option for ‘/admin/default/index’ when in ‘/admin’ ?