Crystal cave is too dark

[Zwatotem]

SuperTux version: 0.6.1, possibly earlier System information: GNU/Linux Parabola

Expected behavior

Dark part of Crystal cave level is dark, but visible to naked eye, so one can activate bonus block in the range of sight and light up the level.

Actual behavior

On some screens dark area is unplayably dark, or even completely black.

Steps to reproduce actual behavior

Play Crystal cave level, go behind the door opened by 2 switches.