Unexpected bug with Evented trigger

I’m having troubles with Evented throwing an odd bug when used with a Promise.

I’ve made a simple service to subscribe to events in my components. It just extends Evented, so we can trigger and listen to events.

import Service from "@ember/service";
import Evented from "@ember/object/evented";
export default Service.extend(Evented);

When used with the following:

return new RSVP.Promise(resolve => {

I get the following error:

 Cannot read property 'apply' of undefined
    at sendEvent (vendor.js:20489)
    ... which is: method.apply(target, params);
    at Class.trigger (vendor.js:32860)

Even if I rewrite the Service to be more explicit, I get the same error:

export default Service.extend(Evented, {
  transitionStart: function() {
  transitionEnd: function() {
  init() {
    this.on("transitionStart", function() {
      //for testing, listen to the event here
      console.log("we received the transition Start event");

and call it via:

return new RSVP.Promise(resolve => {

Why isn’t sendEvent working for me in this context?

trigger(name, ...args) {
    sendEvent(this, name, args);