Automated letsencrypt issuing bad certificate - Fake LE Root X1

Expected behavior

Valid letsencrypt certificate should be issued.

Actual/Current behavior

An invalid certificate is issued by Fake LE Root X1

Steps to reproduce the actual/current behavior

1. Set NODE_ENV=production in .env
2. Add letsencrypt config as per this article.
3. Run keystone
4. Load in browser, no green padlock as certificate is invalid.

If I manually generate the certificate with certbot, then move the keys over, everything works properly.

Environment

Software	Version
Keystone	4.0.0-beta.5
Node	v6.12.3
Ubuntu	16.04