Ember doesn't use custom application adapter

I just updated my Ember app from 1.10 to 1.13 (Ember-CLI and Ember Data too) and wonder, why my application adapter doesn't get used anymore. I've installed the new active-model-adapter add-on accordingly to this documentation.

import ActiveModelAdapter from 'active-model-adapter';
import config from './config/environment';
/* global getSubdomain */

console.log('ActiveModelAdapter loaded?');

export default ActiveModelAdapter.extend({
  host: (config.environment === 'development') ? 'http://' + getSubdomain() + '.example.dev:5000/api' : 'http://' + getSubdomain() + '.example.io/api',
  namespace: 'v1',
  subdomain: getSubdomain()
});

But there aren't any console outputs and all requests go to http://ift.tt/1HoQGbi instead of http://ift.tt/1IOnJe0.

The file is located in /app/adapters/application.js, so everything should be fine.

Are there more breaking changes that I've missed or does Ember need some more configuration to run custom application adapters?