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.

The old category will still apply. For some reason Marriott shows the new category (and points required). When you have enough Points just call the MR hotline and have them attach the 25k points to the reservation and everything will be ok.

Even if you had had the points when you made the reservation it would now look as if you had deposited 30k points for it. However, if you cancelled you would just get the 25k back that you would have deposited originally.

This has happened to me a few times and it has always been easily corrected. In fact if you look at the thread announcing this year's cat changes I even posted a warning about checking reservations for this...

The explanation has usually been there was a back of the house reason to update the reservation, like to give you an UG, and the reservation flipped to the new points total. I feel bad for the people that do not notice or that do not know all you have to do is point this out, and it should not still be happening at least fifteen years after the first time it happened to me, and when it happens to you of course you are going to be concerned/upset, but it winds up being a nothing. The first time this happened to me it was the Niagara Falls Marriott and I called in a panic. The poor woman who answered the phone couldn't get me to a manager fast enough, but the manager explained she had given me an UG, changed my reservation, triggered the charge and corrected it quickly.

Thanks for everyone's reply, just a quick update in case people look for it in the future, I called Marriott Rewards and they attached the certificate at the old rate with no questions asked, so don't be alarmed if this happen to you as well.

This happened to me as well. I made a reservation for this summer a few days before the March 6th cutoff for the devaluation - and when I made the reservation I was indeed given the lower pre-devaluation rate. But when I recently checked the reservation, it showed the higher post-devaluation rate.

Unfortunately, in my case, a call did not resolve the issue. When I called, the agent told me that from his end, it looked like I made the reservation on March 6th (which would be too late). I know this is not correct, but I have no way to prove this. I am wondering if the system somehow re-booked the reservation at the higher rate, with the date for when the higher rate went into effect. Has anyone else experienced this? And any suggestions on what if anything I can do about it?