I booked a hotel in Paris before it went to category 6 (from category 5), but when I check the booking today it went from 25k points per night to 30k points per night, is this supposed to happen? I thought existing bookings shouldn't be impacted by category changes?

In case it makes any difference, I haven't got the points required yet so it is booked without the points, with the aim to get the e-certificate assigned later, but now it looks like I will be stuck with category 6 if I want to keep this booking.