Bug in git remote prune?

Let's say you've got the following tracking branches:

refs/remotes/origin/master refs/remotes/origin/next refs/remotes/origin/ghost

And origin has only "master" and "next" (ghost has been removed upstream).

Further, let's say you've got a refspec of:

[remote "origin"]
  fetch = +refs/heads/master:refs/remotes/origin/master

What should "git remote prune origin" do?

In my opinion, it should prune "next" and "ghost". "ghost" is gone from upstream, so that's obvious. I think "next" should also be pruned because the refspec indicates the user is no longer interested in it.

Currently it doesn't do anything (it only considers "master" per the refspec, which is still on origin, so it doesn't think there is anything to prune).

Thoughts?

j.