Unable to build kernel #263665 "config: illegal option -- I"

[Vladimir Sharun]

Hello FreeBSD comunity,

Got yesterday following issue with #263665:

# make kernel


--------------------------------------------------------------
>>> Kernel build for COBALT started on Sun Mar 23 17:44:45 EET 2014
--------------------------------------------------------------
===> COBALT
mkdir -p /usr/obj/usr/src/sys


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


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


Stop.
make: stopped in /usr/src

The same for GENERIC as well. Emptying src.conf and make.conf doesn't help.
Last kernel succesfully built (the system now runs it) was r263345