[Typo3-debian] Fatal error: Call to undefined function: imagegif()

[Cedric Gaspoz]

Hi, I have installed the debs from http://typo3.sunsite.dk/software/debian/
on my sarge and all work fine. When I make a new Site, I have no problems,
but when I try to open the testsite (which I need to learn more), I always
get the error:
Fatal error: Call to undefined function: imagegif() in
/var/lib/typo3/typo3_src-3.6.1/t3lib/class.t3lib_stdgraphic.php on line 2316

What's wrong?
Thanks
Cedric