Dynamic segment doesn't return value

I want to define a route like the following:

App.Router.map(function(){
  this.resource('clip', {path: ':slug'}, function(){
    this.route('settings');
  });
});

When trying to either visit /some-slug or /some-slug/settings, the params object return empty.

App.ClipIndexRoute = Em.Route.extend({
  model: function(params){
    alert(params.slug);
    return {};
  }
})

Why is that happening? And, more important, what can I do to make it work?

Here’s an sample app replicating this issue: http://jsbin.com/jomuva