Updating DC functional level from 2008 R2 to 2012 problem with RODC DC

Hello,

We upgraded our lab today from dc functional level 2008 r2 to 2012.   We were getting an error (below) stating we couldn't raise it.   We proceeded by demoting/removing our one 2008 R2 RODC DC and that fixed the problem.    The other two DCs in the lab are 2012.

So can you not raise your fomain functional level to 2012 if you either have:

an RODC

or a non 2012 server?

Thanks for the help.  We're preparing for production.

Error:  “The functional level of the domain (or forest) cannot be raised to the requested value, because there exist one or more domain controllers in the domain (or forest) that are at a lower incompatible functional level.”