I am not sure exactly which library is exactly responsible for the issue, but if one looks at this line:

https://github.com/stefanpenner/es6-promise/blob/a5838bd94a76e31ad80ac1685bcd0dbc3d8ce963/dist/es6-promise.js#L1133-L1144

One can see that they are expecting
Object.prototype.toString.call(window.Promise.resolve()) to be [object Promise], but zone.js gives [object Object]

So, I am wondering, should es6-promise (coming from another widget hosted on our page served over their CDN) look for [object Object], or should zone.js have [object Promise] for this toString()