Register multiple vCenter servers to one VUM server?

Greetings,

I've got 2 vCenter servers and one vSphere Update Manager server. Currently, VUM is registered to my older vCenter 4.1 server and I'd like to also register it with my new vCenter 5.1 server, thus using one VUM to patch both of my vSphere environments (ESXi patches only).

Is this possible, or does each vCenter instance require its own dedicated VUM?

Thanks in advance!