diff --git a/whalesong/world/kernel.js b/whalesong/world/kernel.js
index 8f27a40..107645e 100644
--- a/whalesong/world/kernel.js
+++ b/whalesong/world/kernel.js
@@ -377,7 +377,7 @@ DefaultDrawingOutput.prototype.toRawHandler = function(MACHINE, toplevelNode) {
 var StopWhen = function(handler, last_picture) {
     WorldConfigOption.call(this, 'stop-when');
     this.handler = handler;
-    this.last_picture = new ToDraw(last_picture);
+    this.last_picture = last_picture && new ToDraw(last_picture);
 };
 
 StopWhen.prototype = plt.baselib.heir(WorldConfigOption.prototype);
@@ -385,6 +385,6 @@ StopWhen.prototype = plt.baselib.heir(WorldConfigOption.prototype);
 StopWhen.prototype.toRawHandler = function(MACHINE, toplevelNode) {
     var that = this;
     var worldFunction = adaptWorldFunction(that.handler);
-    var lastPictureHandler = that.last_picture.toRawHandler(MACHINE, toplevelNode);
+    var lastPictureHandler = that.last_picture && that.last_picture.toRawHandler(MACHINE, toplevelNode);
     return rawJsworld.stop_when(worldFunction, undefined, lastPictureHandler);
 };
diff --git a/whalesong/world/raw-jsworld.js b/whalesong/world/raw-jsworld.js
index 4e91d25..c878068 100644
--- a/whalesong/world/raw-jsworld.js
+++ b/whalesong/world/raw-jsworld.js
@@ -663,12 +663,16 @@ var rawJsworld = {};
             stopWhen.test(w,
                           function(stop) {
                               if (stop) {
-                                  var handler = stopWhen.last_picture_handler();
-                                  handler.onRegister(top);
-                                  handler._listener(w, oldW, function(v) {
+                                  if (stopWhen.last_picture_handler) {
+                                      var handler = stopWhen.last_picture_handler();
+                                      handler.onRegister(top);
+                                      handler._listener(w, oldW, function(v) {
+                                          Jsworld.shutdown({cleanShutdown: true});
+                                          k2();
+                                      })
+                                  } else {
                                       Jsworld.shutdown({cleanShutdown: true});
-                                      k2();
-                                  })
+                                  }
                               } else { k2(); }
                           });
         };