Rails: Undefined method `flash' for ActionDispatch::Request

I'm trying to write an Ember application in Rails 4, and have decided to go with rails-api for the api controllers, while keeping the application controller intact for a few pages that aren't part of the single-page app. To put it in more concrete terms, here are my controllers: app/controllers/application_controller.rb: class ApplicationController < ActionController::Base protect_from_forgery end