I've seen it happen more than once: you know that you want to play in no-trump, but wonder if it should be a game or a slam contract. You initiate Blackwood with a 4NT bid, and partner's response tells you that slamming is not a good idea. Now you'd like to stop in 5NT, but bidding 5NT sounds like an inquiry about kings, and lands you in 6NT anyway.
The simple solution, so simple it's easily overlooked, is to bid a suit in response to partner's ace-count bid. This should be corrected by partner into 5NT.
† Let's stop this madness.