[U-Boot] Author search of git.denx.de does not work

The following URL doesn't show anything:

http://git.denx.de/?p=u-boot.git&a=search&h=HEAD&st=author&s...

No matter what I put after the "s=", I get nothing. I think it should work, because this URL, which has the same search string, does work:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git&a=searc...