"No commit object added" during clone

[Zygmunt Krynicki]

zyga@w510:~/Scratch$ git clone bzr::lp:lava-server
Cloning into 'lava-server'...
unknown command "commit"
Traceback (most recent call last):map 419/1263
  File "/home/zyga/.local/bin/git-remote-bzr", line 220, in <module>
    commands[argv[0]](argv, shortname, remote_dir)
  File "/home/zyga/.local/bin/git-remote-bzr", line 89, in cmd_list
    for ref, git_sha1 in refs.as_dict().iteritems():
  File "/usr/lib/python2.7/dist-packages/dulwich/repo.py", line 196, in as_dict
    ret[key] = self[("%s/%s" % (base, key)).strip("/")]
  File "/usr/lib/python2.7/dist-packages/dulwich/repo.py", line 267, in __getitem__
    _, sha = self._follow(name)
  File "/usr/lib/python2.7/dist-packages/dulwich/repo.py", line 249, in _follow
    contents = self.read_ref(refname)
  File "/usr/lib/python2.7/dist-packages/dulwich/repo.py", line 225, in read_ref
    contents = self.read_loose_ref(refname)
  File "/home/zyga/.bazaar/plugins/git/refs.py", line 134, in read_loose_ref
    return self.object_store._lookup_revision_sha1(revid)
  File "/home/zyga/.bazaar/plugins/git/object_store.py", line 564, in _lookup_revision_sha1
    self._update_sha_map(revid)
  File "/home/zyga/.bazaar/plugins/git/object_store.py", line 369, in _update_sha_map
    self._update_sha_map_revision(revid)
  File "/home/zyga/.bazaar/plugins/git/object_store.py", line 480, in _update_sha_map_revision
    commit_obj = updater.finish()
  File "/home/zyga/.bazaar/plugins/git/cache.py", line 552, in finish
    raise AssertionError("No commit object added")
AssertionError: No commit object added

bzr-git: trunk, revno 1506, bzr 2.5b4, git 1.7.7.3