Order be specific multiple term_id's / category_id's

Hello everyone,

I’m having trouble to do the following:

I would like to order my loop by post_type and by multiple categories that are listed in my custom taxonomy called “shop_categories”.

Normally, with posts, I would do this:
query_posts('post_type=post&cat=1,2')

But now I would like to do this:
query_posts('post_type=products&taxonomy=shop_categories&cat=1,2'

However, the last one doesn’t work. Does anyone know how I can achieve this?

Hoping for help.