git-gui blame dividing by zero

Hello,

I've not used it before, but I thought I'd give it a go:

 $ git --version
 git version 1.5.1
 $ $ git-gui --version
 git-gui version 0.6.5
 $ git-gui blame HEAD somefile.cc

I just get a window that contains:

divide by zero
divide by zero
    while executing
"expr {100 * $blame_data($w,blame_lines)
			/ $blame_data($w,total_lines)}"
    (procedure "blame_incremental_status" line 4)
    invoked from within
"blame_incremental_status $w"
    (procedure "read_blame_catfile" line 27)
    invoked from within
"read_blame_catfile file6 {} HEAD 
somefile.cc .cm.t .out.loaded_t .out.linenumber_t .out.file_t"

Am I doing something wrong?

Andy