Source-upgrading from FreeBSD 4.9 to 4.11

[patrick]

I'm trying to do a source upgrade from FreeBSD 4.9 to 4.11, but during
the "make buildworld", I get the following:

===> gnu/usr.bin/cvs/cvs
make: don't know how to make stack.c. Stop
*** Error code 2

Stop in /usr/src/gnu/usr.bin/cvs.
*** Error code 1
...

I didn't see any mention of this in the handbook, but do I have to
upgrade to 4.10 first, and then go up to 4.11?

Thanks,

Patrick