Strange behavior of grubby in anaconda (fedora 13)

  Hi!
I am trying to run the following command in anaconda during installation 
of Fedora 13:
/sbin/grubby --update-kernel=`/sbin/grubby --default-kernel` 
--args="console=tty0"
And it does not work - no changes to grub.conf are made. If I run it on 
the system after installation is complete, it works just fine.
Some more information - this command is generated by cobbler snippet 
post_install_kernel_options. I have it as a part of more complicated set 
- the original command uses --agrs="console=tty0 
console=console=ttyS0,9600n8". The second part (with ttyS0) works fine, 
but the first one is dropped. I tried to swap them - the order does not 
matter. I have the same setting working on Scientific Linux without any 
problems.
It is not a cobbler issue - the snippet is rendered properly and also I 
tried to run it manually during post installation logging into the 
system with ssh.
Any comments/ideas why would that happens?

Thanks!

Leon