Openconnect cannot connect to Anyconnect VPN group using -g

I am using openconnect to connect to a VPN. When starting the client as sudo openconnect -v -u anaphory vpn-gw1.somewhere.net, I am able to connect after entering the GROUP and Password.

# openconnect -v -u anaphory vpn-gw1.somewhere.net
[…]
XML POST enabled
Please enter your username and password.
GROUP: [Anyconnect-VPN|CLUSTER-DLCE|Clientless]:CLUSTER-DLCE
POST https://vpn-gw1.somewhere.net
Got HTTP response: HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
[…]

However, when I specify that same group name on the command line, the connection fails with an “Invalid host entry” message.

# openconnect -v -g CLUSTER-DLCE -u anaphory vpn-gw1.somewhere.net
[…]
XML POST enabled
Please enter your username and password.
Password:XML POST enabled
Invalid host entry. Please re-enter.
Failed to obtain WebVPN cookie

Do I need to do any magic to the group name, or how do I find out how to make this work?