ipset version 2.5.0-1 failed to build in oneiric

ipset version 2.5.0-1 failed to build in oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2696921

Details about the rebuild:
http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-20110816-oneiric.html

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2696921/+files/buildlog_ubuntu-oneiric-amd64.ipset_2.5.0-1_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 225 lines into the build log:

rm -rf ipset libipset_ipmap.so libipset_portmap.so libipset_macipmap.so libipset_iptree.so libipset_iptreemap.so libipset_iphash.so libipset_nethash.so libipset_ipporthash.so libipset_ipportiphash.so libipset_ipportnethash.so libipset_setlist.so *.o *~
make[1]: Leaving directory `/build/buildd/ipset-2.5.0'
 debian/rules build
dh_testdir
/usr/bin/make binaries
make[1]: Entering directory `/build/buildd/ipset-2.5.0'
cc -O2 -Wall -Wextra -Waggregate-return -Wbad-function-cast -Wcast-align -Wformat=2 -Wfloat-equal -Winit-self -Winline -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wold-style-definition -Wpacked -Wredundant-decls -Wshadow -Wsign-compare -Wstrict-prototypes -Wswitch-default -Wswitch-enum -Wundef -Wwrite-strings -Wno-missing-field-initializers -Werror -Ikernel/include -I. -DIPSET_VERSION=\"2.5.0\" -DIPSET_LIB_DIR=\"/usr/lib/ipset\" -c -o ipset.o ipset.c
ipset.c: In function 'set_restore':
ipset.c:1366:6: error: variable 'first_pass' set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

make[1]: *** [ipset.o] Error 1
make[1]: Leaving directory `/build/buildd/ipset-2.5.0'
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110821-1024
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/ipset-2.5.0