lua 'grub.run' does not return message text

[edgar . soldin]

When I run

err,msg = grub.run("ls")

only the variable err is filled with the exit code.
msg is still nil .. I saw documentation that grub.run is supposed to 
return the output in the second variable.

I use lua from grub-extras repository
http://bzr.savannah.gnu.org/lh/grub-extras/
checked out yesterday.

What am I doing wrong?

Thanks .. ede