X-ray with door and slab

Closing a door on yourself when underneath an upside down slab will result in you standing up into the slab gaining Xray above yourself.

Steps to reproduce: 

1. Place an upside down slab next to a door and open the door.
2. Crouch underneath the slab and release the crouch button.
3. Position yourself so you are underneath the slab while also inside the door.
4. Close the door on yourself and look up.

Pictures and a video attached.