ambiguous argument '...': unknown revision or path not in the working tree

I've got a strange error message in 'git push':

,----
| % git push
| Counting objects: 47, done.
| Delta compression using up to 2 threads.
| Compressing objects: 100% (24/24), done.
| Writing objects: 100% (24/24), 4.37 KiB, done.
| Total 24 (delta 22), reused 0 (delta 0)
| fatal: ambiguous argument '3bbc6def8a06e4411bee130b811ff9507e90503d:debian/changelog': unknown revision or path not in the working tree.
| Use '--' to separate paths from revisions
| To git+ssh://git.debian.org/git/collab-maint/ncurses.git
|    2fec7db..3bbc6de  HEAD -> upstream
`----

Indeed debian/changelog is not in the working tree, it is not in the current branch (upstream) at all, although it exists in the master branch. Default is to push the current branch:

,----
| % git config --get push.default 
| current
| % git --version
| git version 1.6.6
`----

Despite the error message, the push was apparently successful; the repository I push to can be found at http://git.debian.org/?p=collab-maint/ncurses.git.

Sven