Cannot push to a branch `svn cp'ied`

I have a [minirok.dev] branch, from which I push with bzr-svn to this
[svn trunk]. Recently I branched off minirok.dev at revision 296 into
[minirok.kde4].

  [minirok.dev]: http://chistera.yi.org/~adeodato/bzr/minirok/minirok.dev
  [svn trunk]: https://forja.rediris.es/svn/csl2-minirok/trunk
  [minirok.kde4]: http://chistera.yi.org/~adeodato/bzr/minirok/minirok.kde4

At the same time as I branched off with Bazaar, I did this in the svn
side:

  % svn mkdir https://forja.rediris.es/svn/csl2-minirok/branches
  % svn cp https://forja.rediris.es/svn/csl2-minirok/trunk https://forja.rediris.es/svn/csl2-minirok/branches/kde4

Now doing:

  minirok.kde4% bzr push https://forja.rediris.es/svn/csl2-minirok/branches/kde4

says (after a while with high-CPU usage):

  bzr: ERROR: These branches have diverged. Try using "merge" and then "push".

FWIW, all the bzr:* properties in both SVN trunk and SVN kde4 have the
very same values. And:

  minirok.kde4% bzr missing https://forja.rediris.es/svn/csl2-minirok/branches/kde4
  bzr: ERROR: exceptions.AssertionError: Empty parent added, but child wasn't added !?

  Traceback (most recent call last):
    File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 802, in run_bzr_catch_errors
      return run_bzr(argv)
    File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 758, in run_bzr
      ret = run(*run_argv)
    File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 492, in run_argv_aliases
      return self.run(**all_cmd_args)
    File "/usr/lib/python2.4/site-packages/bzrlib/commands.py", line 768, in ignore_pipe
      result = func(*args, **kwargs)
    File "/usr/lib/python2.4/site-packages/bzrlib/builtins.py", line 3270, in run
      remote_branch)
    File "/usr/lib/python2.4/site-packages/bzrlib/missing.py", line 78, in find_unmerged
      "remote", 3, remote_rev_history)
    File "/usr/lib/python2.4/site-packages/bzrlib/missing.py", line 123, in _get_ancestry
      topo_sorted=False))
    File "/home/adeodato/.bazaar/plugins/svn/repository.py", line 449, in get_ancestry
      for (branch, rev) in self.follow_branch(path, revnum - 1, scheme):
    File "/home/adeodato/.bazaar/plugins/svn/repository.py", line 930, in follow_branch
      assert paths[p][1] is not None, \
  AssertionError: Empty parent added, but child wasn't added !?

This is with rev 826 of the 0.4 branch of bzr-svn.

 affects /products/bzr-svn