PhysicsConstraints.setNumIterations make blender crash

Here’s the deal, when I create physics simulations in BGE I want to be able to increase the iterations-per-frame and substeps but when i try writing a script for it (there is no GUI is there?) it crashes.

The script usually looks like this:
import PhysicsConstraints


And when i execute it blender crashes. I’m running linux with the latest SVN trunk.