How do I remove the host key?

This bug is quite annoying. Especially because it's easy to trigger and the prompt dialog doesn't explaint how to remove the existing key.
http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=106

I already tried 'ssh-keygen -R [host]' with no effect. and according to the bug report this is not how it's done anymore...

Pascal