Should this not be back patched ? The error that's coming because not having this fix is rather very strange and hard to debug for any average individual. I'd almost concluded that one should NEVER use an old psql with a new server even though the warning that comes is not too glaring.
Never mind. I just read the email thread leading to this commit. This wasn't a bug fix per se and that's probably the reason why this was never back patched. The discussion itself looked quite inconclusive as well.