Error When Promoting DRBD Primary

I was having some issues today setting up DRBD on some new SANs. When I would try and promote one of the SANs to primary using this command:

sudo drbdadm -f primary r0

I would get this error:

0: State change failed: (-2) Need access to UpToDate data
Command 'drbdsetup 0 primary' terminated with exit code 17