Egg git interface for emacs, commit empty message

I am using an egg (emacs got git) as the git interface in emacs. Whenever I try to execute commit -amend, I get"GIT-COMMIT-AMEND> Aborting commit due to empty commit message".

This is what I do:

C-u C-x v c

Then a commit buffer appears with the message of my previous commit.

Then after C-c C-cI get the message above: an empty commit message.

I think that earlier I had this behavior with regular commits (as in a non-fix), but I could not remember or find how I solved it.

I tried to edit the post (adding a place somewhere). No work.

I tried to save the buffer before commit, which would not work either (since it C-c C-cis inactive in a buffer other than the commit buffer).

Any clue?