vrf address familiy upgrade

I was wondering if anyone has had experience with the vrf cli upgrade
command that upgrades an existing V4 only VRf to a multi-protocol vrf?

command:

(config)# vrf upgrade-cli multi-af-mode ........

My issue is that it fails to upgrade the my, one of the pre-requisites is
that the
vrf must exist, it does???

thanx as always,

Mike