Prince is partially visible when falling through walls

Steps to reproduce:
1. Make "topless" walls somewhere.
2. Make the Prince fall into them.
3. As he falls, parts of him are occasionally visible.

Illustration video: http://oscomp.hu/depot/sdlpop_prince_visible_through_wall.mkv

Note: The same happens in the original game, but i still think, this should be fixed.