Changing the planning plant in centralized maintenance planning (PM)

We are closing the planning plant where we perform centralized maintenance planning and moving the process to a new plant.

However, when I remove the closed plant from IMG: Enterprise Structure -> Definition -> Plant Maintenance -> Maintain maintenance planning plant

I get an error message in IE01 and IE02 that the closed plant is not defined as a planning plant. This happens no matter what maintenance plant I use.

So how do I change the default maintenance planning plant to the new plant to get rid of this message?

Thanks in advance.