How do I Stop light from going diagonally between tiles

I have a tileset that creates shadows, the problem is that when I place two tiles diagonally some light gets through at the corner, how do I fix this

Here is what I mean:

Not sure on a proper fix, but a temporary fix might be to add some edge tiles in the corners. They could even be transparent as long as they have some collision

0Hayes Thanks, but the player is going to be placing tiles, however I may be able to use this if I can't find a better solution