Ember.js controllers 'needs' syntax

I am using the controller dependency helper needs for my ember controller. I know the basic syntax:

export default Ember.Controller.extend({
  needs: 'post'

and then you can access the dependency controller as controllers.post

But what if you require a controller that is nested:

export default Ember.Controller.extend({
  needs: 'users/show'

How do you access this?