push to empty repository causes error

bzr push over ssh into a new repository that was just bzr init-ed fails as follows:

--- post_push
NEW REVISION!
{'new_revno': 1, 'local_branch': None, 'new_revid': '<email address hidden>', 'target_branch': RemoteBranch(bzr+ssh://bk-internal/data1/bzrroot/internals/), 'source_branch': BzrBranch6('file:///shared/home/df/mysql/bazaar/internals/'), 'tag_conflicts': None, 'old_revid': 'null:', 'old_revno': 0, 'master_branch': RemoteBranch(bzr+ssh://bk-internal/data1/bzrroot/internals/)}

target_branch:
{'_lock_mode': 'w', 'repository': RemoteRepository(bzr+ssh://bk-internal/data1/bzrroot/internals/.bzr/), '_format': <bzrlib.remote.RemoteBranchFormat object at 0x2ad9b69812d0>, '_repo_lock_token': '', '_revision_id_to_revno_cache': None, '_revision_history_cache': None, 'base': 'bzr+ssh://bk-internal/data1/bzrroot/internals/', '_client': <bzrlib.smart.client._SmartClient object at 0x2ad9b5f60810>, '_real_branch': BzrBranch6('bzr+ssh://bk-internal/data1/bzrroot/internals/'), '_lock_token': '0ngy4jvhkuc92t08zf03', '_control_files': None, '_lock_count': 1, '_leave_lock': False, 'bzrdir': <bzrlib.remote.RemoteBzrDir object at 0x2ad9b5c615d0>}

tree name:
bzr: ERROR: exceptions.AttributeError: 'RemoteBranch' object has no attribute '_base'

Traceback (most recent call last):
  File "/usr/lib64/python2.4/site-packages/bzrlib/commands.py", line 834, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/usr/lib64/python2.4/site-packages/bzrlib/commands.py", line 790, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib64/python2.4/site-packages/bzrlib/commands.py", line 492, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib64/python2.4/site-packages/bzrlib/builtins.py", line 861, in run
    stop_revision=revision_id)
  File "/usr/lib64/python2.4/site-packages/bzrlib/decorators.py", line 127, in read_locked
    return unbound(self, *args, **kwargs)
  File "/usr/lib64/python2.4/site-packages/bzrlib/branch.py", line 1558, in push
    _override_hook_source_branch=_override_hook_source_branch)
  File "/usr/lib64/python2.4/site-packages/bzrlib/branch.py", line 1606, in _push_with_bound_branches
    _run_hooks()
  File "/usr/lib64/python2.4/site-packages/bzrlib/branch.py", line 1575, in _run_hooks
    hook(result)
  File "/shared/home/df/.bazaar/plugins/pushtest/__init__.py", line 20, in post_push
    head = push_result.target_branch._base
AttributeError: 'RemoteBranch' object has no attribute '_base'

bzr 1.4dev on python 2.4.3 (linux2)
arguments: ['/usr/bin/bzr', 'push', 'bzr+ssh://bk-internal/data1/bzrroot/internals']
encoding: 'ISO-8859-1', fsenc: 'ISO-8859-1', lang: 'C'
plugins:
  gtk /shared/home/df/.bazaar/plugins/gtk [0.94.0dev0]
  launchpad /usr/lib64/python2.4/site-packages/bzrlib/plugins/launchpad [unknown]
  multiparent /usr/lib64/python2.4/site-packages/bzrlib/plugins/multiparent.py [unknown]
  pushtest /shared/home/df/.bazaar/plugins/pushtest [unknown]
*** Bazaar has encountered an internal error.