bzr nick breaks loom

I started trying to do some development in looms.

First step was to do "bzr loomify" but it told me I needed to give a nickname. So I gave "bzr nick feature".

I then wanted to create a thread which was "upstream" to keep a pristine copy of bzr.dev. However, 'create-thread' only creates a thread above your current one.

So what I wanted was to have the original thread be named "upstream" and my current thread be named "feature".

So my first attempt was to do:
 bzr nick alt-feature

However, after that point all bzr commands fail during the unlock() phase with a traceback similar to:
...
  File "/home/jameinel/dev/bzr/bzr.dev/bzrlib/config.py", line 942, in set_option
    self.branch.unlock()
  File "/home/jameinel/.bazaar/plugins/loom/branch.py", line 658, in unlock
    if dict(state.get_threads_dict())[self.nick][0] != lastrev:
KeyError: u'assert_list'

Is there a way to rename a thread? Since it seemed that the current thread was labeled based on branch nickname I thought "bzr nick" would be the command to use to change it.

Anyway, the only way to get the branch working again seemed to be to use "bzr nick original_name".
(I actually just edited branch.conf manually, but I think it would do the same thing.)