unable to push to packs-based smart server

Bazaar (bzr) 0.92.0.dev.0
  from bzr checkout /afs/isgenesis.com/user/ccd/bzr-packs.rcollins
    revision: 2852
    revid: <email address hidden>
    branch nick: bzr-packs.rcollins
  Python interpreter: /usr/bin/python 2.4.4.final.0
  Python standard library: /usr/lib/python2.4
  bzrlib: /afs/isgenesis.com/user/ccd/bzr-packs.rcollins/bzrlib
  Bazaar configuration: /afs/isgenesis.com/user/ccd/.bazaar
  Bazaar log file: /afs/isgenesis.com/user/ccd/.bzr.log

(same version on both client and server; server is operating against a packs-backend repository)

===

$ time bzr-packs push bzr://gentoo-mirror.isgenesis.com/upstream-portage-tree
bzr: ERROR: Could not understand response from smart server: ('error', "<bound method GraphKnitRepository.leave_lock_in_place of GraphKnitRepository('chroot-47750944724688:///.bzr/repository/')>")

real 5m20.247s
user 3m11.316s
sys 0m2.972s

===

Traceback (most recent call last):
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/protocol.py", line 103, in accept_bytes
    self.request.dispatch_command(req_args[0], req_args[1:])
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/request.py", line 171, in dispatch_command
    self._run_handler_code(self._command.execute, args, {})
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/request.py", line 182, in _run_handler_code
    result = self._call_converting_errors(callable, args, kwargs)
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/request.py", line 193, in _call_converting_errors
    return callable(*args, **kwargs)
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/request.py", line 65, in execute
    return self.do(*args)
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/repository.py", line 51, in do
    return self.do_repository_request(repository, *args)
  File "/home/gentoo-mirror/bzr-packs.rcollins/bzrlib/smart/repository.py", line 171, in do_repository_request
    repository.leave_lock_in_place()
  File "/afs/isgenesis.com/user/ccd/bzr-packs.rcollins/bzrlib/repofmt/pack_repo.py", line 1491, in leave_lock_in_place
    raise NotImplementedError(self.leave_lock_in_place)
NotImplementedError: <bound method GraphKnitRepository.leave_lock_in_place of GraphKnitRepository('chroot-47750944724688:///.bzr/repository/')>