rolling-replace hit a snag on boost

[Pierre Abbat <phma%bezitopo.org@localhost>]

...updated 9793 targets...
/usr/bin/find /usr/obj/pkgsrc/devel/boost-
headers/work/.destdir/usr/pkg/include/boost  -type f -print | /usr/bin/xargs 
/usr/sbin/chown root:wheel
/usr/bin/find /usr/obj/pkgsrc/devel/boost-
headers/work/.destdir/usr/pkg/include/boost  -type d -print | /usr/bin/xargs 
/bin/chmod 755
=> Automatic manual page handling
===> Building binary package for boost-headers-1.52.0nb3
=> Creating binary package /usr/pkgsrc/packages/All/boost-
headers-1.52.0nb3.tgz
===> Replacing for boost-headers-1.52.0nb3
WARNING: experimental target - DATA LOSS MAY OCCUR.
Creating binary package: boost-headers-1.52.0
Creating package /usr/obj/pkgsrc/devel/boost-headers/work/boost-headers-1.52.0
===> Updating using binary package of boost-headers-1.52.0nb3
/usr/pkg/sbin/pkg_add -K /var/db/pkg -U -D /usr/pkgsrc/packages/All/boost-
headers-1.52.0nb3.tgz
pkg_add: Can't open +CONTENTS of depending package boost-1.51.0
pkg_add: 1 package addition failed
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/devel/boost-headers
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/devel/boost-headers
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/devel/boost-headers
*** 'make replace' failed for package boost-headers.
*** Please read the errors listed above, fix the problem,
*** then re-run pkg_rolling-replace to continue.
- boost-headers

The boost packages available in pkgsrc are:
devel/boost-build               distfiles/boost_1_52_0.tar.bz2
devel/boost-docs                licenses/boost-license
devel/boost-headers             meta-pkgs/boost
devel/boost-jam                 wip/boost-test-suite
devel/boost-libs                wip/boost-threadpool
devel/boost-python

The versions installed are:
boost-build-1.52.0
boost-docs-1.52.0
boost-headers-1.52.0
boost-jam-1.52.0nb1
boost-libs-1.52.0
boost-python-1.52.0
boost-1.52.0

What's wrong, and how do I fix it? I'm on DragonFly, if that makes a difference.

Pierre
-- 
sei do'anai mi'a djuno puze'e noroi nalselganse srera