push not resolving commit-ish?

Looks like push can't resolve tags to commits.
Why is that?

linux$ git push -f $PWD v3.10-rc2:refs/heads/vhost-next
error: Trying to write non-commit object
a8c6d53c4d84b3a5eb182758a9cdceceba4691da to branch refs/heads/vhost-next
To /scm/linux
 ! [remote rejected] v3.10-rc2 -> vhost-next (failed to write)
error: failed to push some refs to '/scm/linux'

linux$ git log v3.10-rc2|head -5
commit c7788792a5e7b0d5d7f96d0766b4cb6112d47d75
Author: Linus Torvalds [off-list ref]
Date:   Mon May 20 14:37:38 2013 -0700

    Linux 3.10-rc2


linux$ $ git push -f $PWD
c7788792a5e7b0d5d7f96d0766b4cb6112d47d75:refs/heads/vhost-next
Everything up-to-date