A way to not crunch palette on export?

So I’ve noticed that when exporting as indexed PNG the PM removes all unused colors from the palette, potentially making palette only have as much as few colors. This is bad, because the engine I work with (RPG Maker 2003) for one of my projects accepts only PNGs that have EXACTLY 256 color palette and nothing less or more. How can I prevent PM from crunching the palette on export?

Please see in the project settings (menu File/Project Settings…):


Thank you!​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​