Naming branch starting with a number invokes a crash on finish

[kar]

I have the branch names like name-storyid (so the opposite than default). My branch name starts with "10", and on finish I got an error:

Marking Story 10 as finished...
/var/lib/gems/1.8/gems/git-pivotal-0.8.0/bin/../lib/commands/finish.rb:34:in `finished_state': undefined method `story_type' for nil:NilClass (NoMethodError)
    from /var/lib/gems/1.8/gems/git-pivotal-0.8.0/bin/../lib/commands/finish.rb:15:in `run!'
    from /var/lib/gems/1.8/gems/git-pivotal-0.8.0/bin/git-finish:7

So I believe it took the "10" thinking that it's a story number.