--- a/src/PhysicsObject.cc	Mon Dec 08 15:59:33 2008 +0000
+++ b/src/PhysicsObject.cc	Mon Dec 08 16:01:49 2008 +0000
@@ -247,7 +247,7 @@
         setPosition (newPosition);
 
         // the following may delete this object, so it must be the last thing called
-        onCollision(collisionPoint, NULL);
+        onCollision(collisionPoint);
 
         return;
     }