git describe --contains doesn't work properly for a commit

Hi,
I have just encountered an old kernel git commit:
commit c854363e80b49dd04a4de18ebc379eb8c8806674
Author: Dave Chinner <david@fromorbit.com>
Date:   Sat Feb 6 12:39:36 2010 +1100

    xfs: Use delayed write for inodes rather than async V2
[...]

which cannot be described properly: $ git describe --contains c854363e80b49dd04a4de18ebc379eb8c8806674 fatal: cannot describe 'c854363e80b49dd04a4de18ebc379eb8c8806674'

but it seems to find a tag on which the commit is based: $ git describe c854363e80b49dd04a4de18ebc379eb8c8806674 v2.6.33-rc4-49-gc854363e80b4

if I follow parents
sha=c854363e80b49dd04a4de18ebc379eb8c8806674; 
while true
do 
	parent=$(git show --format=%P $sha | head -1)
	echo $sha $parent
	git describe --contains $parent && break
	sha=$parent
done
c854363e80b49dd04a4de18ebc379eb8c8806674 777df5afdb26c71634edd60582be620ff94e87a0
fatal: cannot describe '777df5afdb26c71634edd60582be620ff94e87a0'
777df5afdb26c71634edd60582be620ff94e87a0 d5db0f97fbbeff11c88dec1aaf1536a975afbaeb
fatal: cannot describe 'd5db0f97fbbeff11c88dec1aaf1536a975afbaeb'
d5db0f97fbbeff11c88dec1aaf1536a975afbaeb 388f1f0c346b533b06d8bc792f7204ebc3e4b7da
v2.6.34-rc1~278^2~14

I am using: $ git --version git version 2.1.4

but the same seems to be the case with older git version (1.8.5.6). $ git rev-list c854363e80b49dd04a4de18ebc379eb8c8806674..v2.6.34 | wc -l 11648

So there seems to be a line between the two commits AFAIU.

Is the history somehow broken or is it a bug in git?