Iron Router error

routes.js

var A = RouteController.extend({
  onBeforeAction: function() {
    console.warn('A');
    this.next();
  }
});
var B = A.extend({
  onBeforeAction: function() {
    console.warn('B');
    this.next();
  }
});
Router.route('extendTest', {
  controller: B
});
Router.go('extendTest');