Facebook ID changes when the user changes their profile photo

Hi, has anyone else solved the issue of getting the facebook Id to identify the user. See article for more info. When the user changes their profile photo the Facebook ID changes :frowning:

https://chatbotsmagazine.com/fb-messenger-bot-how-to-identify-a-user-via-page-app-scoped-user-ids-f95b807b7e46#.hy0lt4h0o