Map expansion not in center

When expanding a map in the carthography table, the newly expanded map is not centered.

What I expected to happen was:

I expected when expanding a map in the carthography table, the 'old map' would be in the center of the new one.

What actually happened was:

The map would be expanded from any of the cornes (in the screenshots it is expanded from the down right corner, but I've seen it expand from the down left corner as well).

Steps to reproduce:

1. Create a new world.

2. On said world, create a map.

3. Look at the map.

4. Expand the map in the carthography table.

5. Look at the new map and see that it isn't centered.