pdisk not updating disk label?

I'm trying to update an old G4 tower from netbsd 8.1 to HEAD,
using pretty much the same process I successfully used on my
Cube.  I wanted to rearrange the partitioning though: I had
a separate /usr partition before and I've thought better of
that.  So I went into pdisk, deleted the old netbsd partitions,
made new ones, wrote out the map and quit.  Now I have a
partition map that's what I want according to pdisk, but
disklabel (and therefore also sysinst) are still seeing the
old layout.  This confuses me a great deal, because I'm
certain the disklabel updated automatically when I was doing
this on the Cube.  None of the available documentation suggests
any extra step is needed, and indeed what it mostly does is
warn against messing with the disklabel if you don't want to
lose the ability to boot macOS.  (macOS is still there on half
the disk, and it still boots, and I'd rather not trash it.)

Can anyone get me out of this fix?  The only thing I could
think of was to reboot in case the disklabel was somehow
cached in memory, but unsurprisingly that didn't help.

			regards, tom lane