Undefined instance method "respond_to" in Rails 5 API Controller

In rails 5 created with --api I have an error

NoMethodError (undefined method `respond_to' for #<Api::MyController:0x005645c81f0798>
Did you mean?  respond_to?):

However, in the documentation for rails 4.2 it says http://edgeguides.rubyonrails.org/4_2_release_notes.html

respond_with and the corresponding class-level respond_to have been moved to the responders gem. Add gem 'responders', '~> 2.0' to your Gemfile to use it:

Instance-level respond_to is unaffected:

And I'm calling the instance method. What's the matter?

class ApplicationController < ActionController::API
end

# ...
class Api::MyController < ApplicationController

  def method1
    # ...
    respond_to do |format|
      format.xml { render(xml: "fdsfds") }
      format.json { render(json: "fdsfdsfd" ) }
    end