buildkernel fails on head

I'm trying to build the current FreeBSD kernel, and that's what I get:

% sudo make buildkernel

--------------------------------------------------------------
>>> Kernel build for GENERIC started on Sun Oct 26 01:39:13 MSK 2014
--------------------------------------------------------------
===> GENERIC
mkdir -p /usr/obj/usr/src/head/sys

--------------------------------------------------------------
>>> stage 1: configuring the kernel
--------------------------------------------------------------
cd /usr/src/head/sys/amd64/conf;  
PATH=/usr/obj/usr/src/head/tmp/legacy/usr/sbin:/usr/obj/usr/src/head/tmp/legacy/usr/bin:/usr/obj/usr/src/head/tmp/legacy/usr/games:/usr/obj/usr/src/head/tmp/legacy/bin:/usr/obj/usr/src/head/tmp/usr/sbin:/usr/obj/usr/src/head/tmp/usr/bin:/usr/obj/usr/src/head/tmp/usr/games:/sbin:/bin:/usr/sbin:/usr/bin  
config  -d /usr/obj/usr/src/head/sys/GENERIC  -I '/usr/src/head/sys/amd64/conf' 
'/usr/src/head/sys/amd64/conf/GENERIC'
config: illegal option -- I
usage: config [-CgmpV] [-d destdir] sysname
       config -x kernel
*** Error code 64

Stop.
make[1]: stopped in /usr/src/head
*** Error code 1

Stop.
make: stopped in /usr/src/head


is there a workaround for that? Is the kernel build broken?

-- 
wbr, Maxim Filimonov
che_at_bein.link