mount -ur doesn't work on NetBSD 5.0.2

[Michael Felke <mi.fe%web.de@localhost>]

Hello,

we started to setup a new release of our netbsd server with NetBSD 5.0.2 
in stead of 4.0.1, as we have done last time.
Everything went well, until we tried to lock our root partion with 
"mount -ur /" again, after making it writeable with "mount -uw /".
Mount_ffs always complains that the operation is not supported, but we 
are using it since NetBSD 2.0, our first NetBSD based server. Forcing it 
work with "mount -urf /" doesn't work also.
We couldn't find something about a change of the ffs's option update 
behavior in the release notes of NetBSD 5.0.x.
Is this an indented change made to the GERNERIC kernel, then we need 
some help how to deactivate this new feature, or is it a bug, so must 
perhaps change back to 4.0.1.
The server is build on a i386 system and uses the raid device in level 1.

sincerely
Michael Felke