gbp buildpackage で --git-pbuilder-options='-sa' で -sa が渡せない

[henrich]

$ gbp buildpackage --git-pbuilder --git-pbuilder-options='-sa'  --git-pristine-tar-commit  --git-upstream-tag=upstream/1_2.2.4
gbp:info: Orig tarball 'xfonts-mplus_2.2.4.orig.tar.xz' not found at '../tarballs/'
gbp:info: Building with (cowbuilder) for sid
gbp:info: Exporting 'HEAD' to '/home/henrich/src/pkg-fonts/build-area/xfonts-mplus-tmp'
gbp:info: Moving '/home/henrich/src/pkg-fonts/build-area/xfonts-mplus-tmp' to '/home/henrich/src/pkg-fonts/build-area/xfonts-mplus-2.2.4'
Building with cowbuilder for distribution sid
I: using cowbuilder as pbuilder
dpkg-buildpackage: source package xfonts-mplus
dpkg-buildpackage: source version 1:2.2.4-1
dpkg-buildpackage: source distribution unstable
dpkg-buildpackage: source changed by Hideki Yamane <henrich@debian.org>
 dpkg-source --before-build xfonts-mplus-2.2.4
dpkg-source: info: applying fix-package-contains-timestamped-gzip.patch
dpkg-source: info: applying 0002-remove-unnecessary-backup-lines.patch
dpkg-source: info: applying 0003-rename-fonts.alias-to-xfonts-mplus.alias.patch
 fakeroot debian/rules clean
dh clean --parallel
   dh_testdir -O--parallel
   dh_auto_clean -O--parallel
   dh_clean -O--parallel
 dpkg-source -b xfonts-mplus-2.2.4
dpkg-source: info: using source format '3.0 (quilt)'
dpkg-source: info: building xfonts-mplus using existing ./xfonts-mplus_2.2.4.orig.tar.xz
dpkg-source: info: building xfonts-mplus in xfonts-mplus_2.2.4-1.debian.tar.xz
dpkg-source: info: building xfonts-mplus in xfonts-mplus_2.2.4-1.dsc
 dpkg-genchanges -S >../xfonts-mplus_2.2.4-1_source.changes
dpkg-genchanges: not including original source code in upload
 dpkg-source --after-build xfonts-mplus-2.2.4
dpkg-source: info: unapplying 0003-rename-fonts.alias-to-xfonts-mplus.alias.patch
dpkg-source: info: unapplying 0002-remove-unnecessary-backup-lines.patch
dpkg-source: info: unapplying fix-package-contains-timestamped-gzip.patch
dpkg-buildpackage: binary and diff upload (original source NOT included)
cowbuilder: invalid option -- 's'
Unhandled option
gbp:error: 'git-pbuilder' failed: it exited with 1

--saとすれば通る、が、実際には -sa は渡されていない。