Trouble getting routes & link_to working

gistfile1.rb

routes.rb
=================
resources :groups do
   member do
     post 'join'
     put 'add_contact'
   end
end

When I do "bundle exec rake routes" I get "add_contact_group" -> /groups/:id/add_contact

I'd like to have /groups/:id/add_contact/:id

so I can pass both group and contact to the add_contact action.

Any hints?