Menu description not visible

Hello. First of all thank you for this great theme!

I’ve found a strange behaviour in the site menu: menu descriptions are not showing at all. And it’s not a CSS problem. I looked at the source code of the page and the description texts simply are not there!

I only have

<li id="menu-item-402" class="menu-item menu-item-type-post_type menu-item-object-page"><a href="..."> Name</a></li>

There is supposed to be a

<br /><span class="menu-desc">Descripcion</span>

just before the closing A tag. But it’s not rendered.

Which can be the problem?

Hope somebody can help us and solve the mistery! Thanks in advance.