Creating attachments using git-format-patch

Hi,

I've been trying to start using git-format-patch together with git-send-email,
but I've encountered some problems. The mailinglist I want to send the patches
to, requires patches to be sent as attachments. So, I tried using the --attach
option of git-format-patch.
However its output does not seem to generate output which Thunderbird or Mutt
recognize as attachments. Has anyone noticed similar problems or am I using it
incorrectly?

I'm doing it as follows:
takis@poseidon:/usr/local/src/ffmpeg-pi$ git-format-patch --attach HEAD^
0001-Modify-av_pkt_dump-and-av_hex_dump-to-be-av_logish.patch
takis@poseidon:/usr/local/src/ffmpeg-pi$ git-send-email
0001-Modify-av_pkt_dump-and-av_hex_dump-to-be-av_logish.patch


Mutt shows a message containing:
This is a multi-part message in MIME format.
--------------1.5.0.1.226.g7bd59
Content-Type: text/plain; charset=UTF-8; format=fixed
Content-Transfer-Encoding: 8bit
...
--------------1.5.0.1.226.g7bd59
Content-Type: text/x-patch;
 name="514f2915144861b6d69ef54bd8d392aa8b3a00e6.diff"
Content-Transfer-Encoding: 8bit
Content-Disposition: inline;
 filename="514f2915144861b6d69ef54bd8d392aa8b3a00e6.diff"
...

But it does not look like an attachment. Same happens when reading the email
with Thunderbird: everything appears inline.

Any suggestions?

With friendly regards,
Takis