Sort order wishlist

I would like to know how i can change the sort order to A-Z in de customers wishlist.

Looked in addons/wishlist/include/customer/wishlist.php but could not find a select query.

Cs-cart version 1.3.5-SP2

I’ve tried to add

{if !$no_sorting}
{include file="products_pages/sorting.tpl"}

to /skins/default_blue/customer/addons/wishlist/wishlist.php, it does display the sort options and produces index.php?target=wishlist&sort_by=product&sort_order=asc, but is does not sort the products.

Does someone know what i still need to change?