diff --git a/src/com/seefurst/towersofhanoi/boardobjects/Board.scala b/src/com/seefurst/towersofhanoi/boardobjects/Board.scala
index f32dc33..8740ec4 100644
--- a/src/com/seefurst/towersofhanoi/boardobjects/Board.scala
+++ b/src/com/seefurst/towersofhanoi/boardobjects/Board.scala
@@ -25,14 +25,13 @@ class Board(numberOfDisksPerPole: Int) {
    def moveDisk(source: Int, dest: Int) = {
      //System.out.println("calling move disk, beginning pole: " + source + " dest pole: " + dest)
      val sourcePole = poles(source) //index
-     val sourceDisk = sourcePole.removeDisk()
-     //System.out.println("source disk: " + sourceDisk)
-     if (sourceDisk == null ) throw new IllegalStateException;
-     
      val destPole = poles(dest) //index
-     destPole.addDisk(sourceDisk)
-     
-   }
+     val sourceDiskOption = sourcePole.removeDisk()
+     sourceDiskOption match {
+       case Some(sourceDisk) => destPole.addDisk(sourceDisk)
+       case None => throw new IllegalStateException;
+     }
+  }
    
    def isFinished: Boolean = {
      poles(poles.length - 1).numberOfDisksOnPole == numberOfDisksPerPole
diff --git a/src/com/seefurst/towersofhanoi/boardobjects/Pole.scala b/src/com/seefurst/towersofhanoi/boardobjects/Pole.scala
index d7c8cf1..60709e1 100644
--- a/src/com/seefurst/towersofhanoi/boardobjects/Pole.scala
+++ b/src/com/seefurst/towersofhanoi/boardobjects/Pole.scala
@@ -29,11 +29,11 @@ class Pole(numberOfDisks: Int) {
     else throw new IllegalArgumentException("disk of size: " + disk.size + " is not allowed on this pole: " + this)
                                            
   }
-  def removeDisk(): Disk = {
+  def removeDisk(): Option[Disk] = {
     try {
-      disks.pop();
+      Some(disks.pop());
     } catch {
-      case e: EmptyStackException => null // use Option????
+      case e: EmptyStackException => None // use Option????
     }
   }