Quick KDE cvs question

[csj]

Thanks to Thomas Schoepf's deb sources, I have what appears to be the 
3.0 branch of cvs KDE. I now feel like upgrading to 3.1 beta. What's the
cvs update line to upgrade from 3.0 to 3.1? The following (obviously)
doesn't work:

cvs -z4 update -dP