Forwarding to Different Port Replaces the Host Header

We use F5 in front of an AWS ALB for firewall purposes. In our virtual server, we forward our https requests to port 85. When the request arrives at our web tier, the request has the host header of our external url with ":85" appended to it. We want the behaviour to be when the request is forwarded, even to a different port, the host header remains the same in order for OpenID to work correctly.

Please let me know if there is a workaround for this, and thanks in advance.