ember-i18n : TypeError: app[initializerType] is not a function

I've been installing ember-i18n on a working Ember project. (http://ift.tt/1kRLqqq)

After registering an initializer app/initializers/i18n.js :

export default {
  name: 'i18n',

  after: 'ember-i18n',

  initialize: function(_, app) {
    app.inject('model', 'i18n', 'service:i18n')
  }
};

And relaunching the server, I get this error in the console :

app[initializerType] is not a function

Do you have any idea ?