Possible bug in --short option of git-rev-list

From git tree

$ git rev-parse v1.5.1.1 HEAD
c5ec6d00eb063f547e314fdf8a1d8cf09472da6b
744747ef1d75c85fb3a1785cb08d36497128d3d3
$ git rev-parse --short v1.5.1.1 HEAD
c5ec6d0
744747e
fatal: Needed a single revision
$

Output is correct, but at the end an (bogus?) error is reported an
git-rev-parse command exits with error code.

Marco