I wrote:
> Indeed, but I concur with the OP that 8.5.1.4 doesn't really expend enough
> words on this point.
After a bit more thought, I committed
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=540849814cdc22ea025777d374ff6705b4d64a0f
regards, tom lane