[Typo3] How to keep transparency in gif-files?

[Bert Hiddink]

Hello!

I am working with small gifs as thumbnails which background is tranpsparent:
http://bendoo.nl/fileadmin/original_bottle.gif

However, when IM makes copies of these gifs to "/typo3temp/pics/" 
transparency disappears and replaced with a dark background.
http://bendoo.nl/fileadmin/typo3_bottle.gif

How can I keep these thumbs transparent when created on-the-fly by IM 4.2.9?

Any ideas?

Many thanks in advance!!!!

grt,
-brt

-- 
Bert Hiddink
hiddink at bendoo.nl
BENDOO e-work solutions
http://www.bendoo.nl
Harterinkdijk 8, 7065 AR SINDEREN
The Netherlands
Tel. 0315 244525