"git log -5 --follow" returns too few commits

Hi,

Using either git 1.5.5.4 or the current master, on my system the command

git log -5 --follow some-file

often returns fewer than 5 commits, even when

git log --follow some-file

returns more than 5.  This behavior occurs even for some files which have 
never been renamed.  Is this a bug, or is this the expected behavior for some 
reason?

Best wishes and thanks,

-Andy