Hostnames not passing

We are trying to get Argo Tunnel running for our domain and the tunnel does establish and I can see that the requests are getting passed to my server through Argo. The problem is that we are running multiple domain names from the same IP address and for some reason the hostname is not getting passed.

We are getting a 400 Bad Request - Invalid Hostname response from IIS. In the debug logs for cloudflared I can see the request and it doesn’t seem to be showing the actual Host header.

How can we get this to work with Argo Tunnel?