Upgrading 9.1-BETA1 -> 9.1-RC1

[Maarten Billemont]

I've installed a FreeBSD server using the BETA1 release because RC1 was delayed.  I notice the 9.1-RC1 is available now, so I thought I'd upgrade ASAP.

The following command, however, fails me:

freebsd-update -r 9.1-RC1 upgrade
Looking up update.FreeBSD.org mirrors... 3 mirrors found.
Fetching metadata signature for 9.1-BETA1 from update4.FreeBSD.org... failed.
Fetching metadata signature for 9.1-BETA1 from update3.FreeBSD.org... failed.
Fetching metadata signature for 9.1-BETA1 from update5.FreeBSD.org... failed.
No mirrors remaining, giving up.

Upon inspection of the code, it appears BETA1's ssl.pub cannot be found at any of the mirrors, and as such the process aborts.

The release notes for RC1 specifically mention freebsd-update.

How do I perform a correct update to RC1, and why is the freebsd-update flow failing me or not supported?

Thanks!