bmake prevent to cross-compile 9/stable from a -current host

Hi,

I can't build 9-stable (or 9.0, 9.1) from my -current host machine
since the switch to bmake.
I've solved this problem by rebuilding my -current host with
WITHOUT_BMAKE, but I would to know if it's a known bug or a new
expected behavior ?

Thanks,

Olivier