How do I launch nextjs app with https in production?

I am writing a nextjs application. I need to launch it with https because the crypto module requires a secureContext. I have nginx setup with https to proxy requests to the nextjs app as https.

I have tried adding --experimental-https in my packages.json to the next start, but this gives the error:

error: unknown option '--experimental-https'

This flag only seems to work in dev mode.