say that I have these routes:
scope \'(:locale)\', :locale => /en|de/ do mount Users::Engine => \"users\", as: \'users_engine\' end
I think I have found a solution for that...
Just use the url_options-method in your application_controller.rb-File (see link below)
See: https://stackoverflow.com/a/18299975/603126
Hope it helps!
Regards
Philipp