xboard: No value provided for argument -firstChessProgram

Hi,

I'm getting the Subject message when I execute 'xboard' from the command line. Unfortunately, the man page and web page don't offer much useful information about what argument is valid for this option. If I try this:

xboard -fcp gnuchess

or this:

xboard -fcp -gnuchessx

I get the same message.

Relevant version information:

% xboard --version
xboard version 4.8.0

% gnuchess --version
GNU Chess 6.2.2

Host platform is FreeBSD 10.2.

Any assistance is greatly appreciated.

Thanks,
dan