Undefined method 'register_engine' while trying to install Ember to Rails

I started learning Ember.js using Rails as back-end, and created a test project. So, first I removed turbolinks from app and added the following gems to Gemfile:

gem 'ember-rails'
gem 'ember-source', '~> 1.8.1'
gem 'emblem-rails'

and bundled them. Next, I ran

$ rails g ember:bootstrap -n App --javascript-engine js

and it has returned me the following error:

/home/alex/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/emblem-rails-0.2.2/lib/emblem/rails/engine.rb:7:in 
`block in <class:Engine>':
    undefined method `register_engine' for nil:NilClass (NoMethodError)

Is the problem that something can be deprecated? I'm following the tutorial written in 2014.