Session cookie key has [“ prepended

I recently upgraded to from 7.1.2 and my session stopped working. Looking at the cookie that gets generated for the session, the key is [“_app_session.

I tried explicitly setting the key with config.session_store but I’m still getting the same result. Anyone know where is the extra [“ is coming from?

Thanks, Jay

Never mind, seems to be a rack 3/phusion incompatibility, see here