Ember Simple Auth isn't using the custom authoriser to add headers

I cannot establish why Ember Simple Auth isn't using the custom authoriser function authorise to add my token to the jQuery AJAX request headers.

I have followed the instructions in the documentation.

Here is my custom authoriser code:

/* Imports */
import Ember from 'ember';
import Base from 'simple-auth/authorizers/base';

/* Puddl Authorizer */
var Authorizer = Base.extend({
    /* Authorize Outgoing Requests */
    authorize: function(jqXHR/*, requestOptions*/) {

        console.log('Authorize');

        /* Add Token To jQuery Request */
        jqXHR.setRequestHeader('Authorization', 'Token '+this.session.content.token);
    },
    init: function() {
    }
});

/* Exports */
export default {
    name: 'Authorizer',
    before: 'simple-auth',
    initialize: function(Container) {
        Container.register('authorizer:custom', Authorizer);
};

I have added the following to the environment config file:

    ENV['simple-auth'] = {
        authorizer: 'authorizer:custom',
        store: 'simple-auth-session-store:local-storage',
        crossOriginWhitelist: [
            'http://localhost/'
        ]
    };

Can anybody help me work this out?