diff --git a/packages/flutter/lib/src/widgets/framework.dart b/packages/flutter/lib/src/widgets/framework.dart
index 8638bad53b..4f7b2d9361 100644
--- a/packages/flutter/lib/src/widgets/framework.dart
+++ b/packages/flutter/lib/src/widgets/framework.dart
@@ -377,8 +377,13 @@ abstract class Widget {
 
   void remove() {
     walkChildren((Widget child) {
-      if (child._generation <= _generation)
+      if (child.isFromOldGeneration || !isFromOldGeneration) {
+        assert(child.parent == this);
         child.remove();
+      } else {
+        // if it's from the current generation and we're not, it means it's been moved somewhere else in the tree already and isn't really our child anymore
+        assert(child.parent != this);
+      }
     });
     _renderObject = null;
     setParent(null);
diff --git a/packages/unit/test/widget/duplicate_key_test.dart b/packages/unit/test/widget/duplicate_key_test.dart
new file mode 100644
index 0000000000..a3a8e75a01
--- /dev/null
+++ b/packages/unit/test/widget/duplicate_key_test.dart
@@ -0,0 +1,51 @@
+import 'package:sky/src/widgets/framework.dart';
+import 'package:sky/src/widgets/basic.dart';
+import 'package:test/test.dart';
+import 'widget_tester.dart';
+
+class Item {
+  GlobalKey key1 = new GlobalKey();
+  GlobalKey key2 = new GlobalKey();
+  String toString() => "Item($key1, $key2)";
+}
+List<Item> items = [new Item(), new Item()];
+
+class StatefulLeaf extends StatefulComponent {
+  StatefulLeaf({ GlobalKey key }) : super(key: key);
+  void syncConstructorArguments(StatefulLeaf source) { }
+  void test() { setState(() { }); }
+  Widget build() => new Text('leaf');
+}
+
+class KeyedWrapper extends Component {
+  KeyedWrapper(this.key1, this.key2);
+  Key key1, key2;
+  Widget build() {
+    return new Container(
+      key: key1,
+      child: new StatefulLeaf(
+        key: key2
+      )
+    );
+  }
+}
+
+Widget builder() {
+  return new Column([
+    new KeyedWrapper(items[1].key1, items[1].key2),
+    new KeyedWrapper(items[0].key1, items[0].key2)
+  ]);
+}
+
+void main() {
+  test('duplicate key smoke test', () {
+    WidgetTester tester = new WidgetTester();
+    tester.pumpFrame(builder);
+    tester.findWidget((widget) => widget is StatefulLeaf).test();
+    tester.pumpFrameWithoutChange();
+    Item lastItem = items[1];
+    items.remove(lastItem);
+    items.insert(0, lastItem);
+    tester.pumpFrame(builder); // this marks the app dirty and rebuilds it
+  });
+}