isNearBorder() doesn't work as expected when using windowZoom

TestBorder.java

package online.app2;

import ch.aplu.android.*;
import android.graphics.Color;

public class TestBorder extends GameGrid
{
  public TestBorder()
  {
     super(true, windowZoom(200));
  }

  public void main()
  {
    addActor(new Ghost(), new Location(50,50));
    setSimulationPeriod(20);
    doRun();
  }
}

class Ghost extends Actor
{
  public Ghost() {
     super("ghost");
  }

  public void act() {
    //if (isMoveValid())  //the commented out way, it works
      move();
    // else 
    if (isNearBorder()) //FIXME: always returns false
      turn(180);
  }
}