Can't use ediff from *cvs* buffer in emacs on potato

[Eric House <fixin@peak.org>]

I'm using emacs and cvs on a stock potato system (updated about a week
ago).

I'd *like* to be using ediff to compare revisions after doing a M-x
cvs-update, but it doesn't work.  I get this error in the minibuffer:

Something went wrong retrieving revision: nil: 1

Plain old vanilla diff works just fine from the *cvs* buffer.

Any ideas what's up, or on how to debug it?

Thanks,

--Eric House

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