W3C Error : Element ul not allowed as child of element ul in this context.

Hello,

I use better exposed filters to display a taxonomy filter select list as a nested checkboxes tree.

But BEF output incorrect HTML for it resulting in a W3C Error :

Element ul not allowed as child of element ul in this context.

By looking at the code, I can see something like that :

...<ul class="bef-tree"><ul class='bef-tree-child bef-tree-depth-0'>...

This is wrong ! A ul element cannot be directly under a ul element. There should be a li between them.

Regards,

Alex