svn error during 'make buildkernel'?

I updated my /usr/src with subversion from ports:

% pkg info | grep subver
subversion-1.7.9_1             Version control system

'make buildworld' completed as expected.  'make buildkernel'
seems to complete, but I'm seeing

:> hack.c
cc  -shared -nostdlib hack.c -o hack.So
rm -f hack.c
MAKE=make sh /usr/src/sys/conf/newvers.sh MOBILE
svn: E155036: The working copy at '/usr/src'
is too old (format 29) to work with client version '1.8.0 (r1490375)' (expects format 31). You need to upgrade the working copy first.

cc  -c -O -pipe -march=core2 -std=c99 -g -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual  -Wundef -Wno-pointer-sign -fformat-extensions  -Wmissing-include-dirs -fdiagnostics-show-option   -nostdinc  -I. -I/usr/src/sys -I/usr/src/sys/contrib/altq -I/usr/src/sys/contrib/libfdt -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000  -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-sse -msoft-float -ffreestanding -fstack-protector -Werror  vers.c
linking kernel.debug
   text    data     bss     dec     hex filename
7688841  617455  595272 8901568  87d3c0 kernel.debug
objcopy --only-keep-debug kernel.debug kernel.symbols
objcopy --strip-debug --add-gnu-debuglink=kernel.symbols kernel.debug kernel
--------------------------------------------------------------
>>> Kernel build for MOBILE completed on Sat Aug  3 13:50:54 PDT 2013
--------------------------------------------------------------

Why is svn being run during 'make buildkernel'?  More importantly,
why is the freshly built svn in /usr/obj being invoked when it 
has not previously been installed and so /usr/src may indeed be
in a older, yet valid, format?

-- 
Steve