fatal: cannot store pack file (git 1.6.0.2 + sshfs)

I'm getting the following when running git on a partition mounted with
sshfs:

$ git pull
remote: Counting objects: 304, done.
remote: Compressing objects: 100% (256/256), done.
remote: Total 260 (delta 103), reused 0 (delta 0)
Receiving objects: 100% (260/260), 26.62 MiB | 3979 KiB/s, done.
Resolving deltas: 100% (103/103), completed with 32 local objects.
error: unable to write sha1 filename .git/objects/pack/pack-dc5c3614e795918f457a2f98a58f10134ebf246b.pack: Operation not permitted

fatal: cannot store pack file
fatal: index-pack failed

git pull worked fine in the same repository yesterday (new files where
committed in the meantime).

I'm not sure if this is a problem in git or in sshfs (or somewhere
else).

Any ideas what the problem could be?

Thanks,

-- 
Jhair