"vncserver -compatiblekbd" fails with "Unrecognized option: -compatiblekbd"

I found that when I connect to my computing cluster via vnc Alt-x is not recognized correctly asM-. I tried vncserver -compatiblekbd but I get Unable to start Xvnc, exiting Actually once my session was started and in the log I found: Fatal server error: Unrecognized option: -compatiblekbd How can I pass this option to vncserver and get the correct mapping of Alt+x ?