diff --git a/Mesh_3/demo/Mesh_3/MainWindow.h b/Mesh_3/demo/Mesh_3/MainWindow.h
index 4b597677ced..a5fc53d55b5 100644
--- a/Mesh_3/demo/Mesh_3/MainWindow.h
+++ b/Mesh_3/demo/Mesh_3/MainWindow.h
@@ -33,8 +33,6 @@ public:
   MainWindow(QWidget* parent = 0);
   ~MainWindow();
 
-  Viewer* getViewer() { return viewer; }
-        
 public Q_SLOTS:
   void updateViewerBBox();
   void open(QString filename);
diff --git a/Mesh_3/demo/Mesh_3/Volume_planes_plugin.cpp b/Mesh_3/demo/Mesh_3/Volume_planes_plugin.cpp
index f4b4aea3612..37b9a8c1951 100644
--- a/Mesh_3/demo/Mesh_3/Volume_planes_plugin.cpp
+++ b/Mesh_3/demo/Mesh_3/Volume_planes_plugin.cpp
@@ -13,7 +13,6 @@
 #include <CGAL_demo/Scene_interface.h>
 #include <CGAL_demo/Scene_item.h>
 #include <CGAL_demo/Viewer.h>
-#include "MainWindow.h"
 
 #include <QAction>
 #include <QMenu>
@@ -173,11 +172,8 @@ public:
     connect(planeSwitch, SIGNAL(triggered()), this, SLOT(selectPlanes()));
     
     // evil
-    MainWindow* mwTmp;
-    if( !(mwTmp = dynamic_cast<MainWindow*>(mw)) ) {
-      std::cerr << "Volume_planes_plugin cannot init mousegrabber" << std::endl;
-    }
-    Viewer* v = mwTmp->getViewer();
+    Viewer* v = mw->findChild<Viewer*>("viewer");
+    CGAL_assertion(v != 0);
     pxr_.setViewer(v);
     connect(v, SIGNAL(pointSelected(QPoint)), &pxr_, SLOT(update(QPoint)));
 
diff --git a/Polyhedron/demo/Polyhedron/Scene_edit_polyhedron_item.cpp b/Polyhedron/demo/Polyhedron/Scene_edit_polyhedron_item.cpp
index c3036bdeca9..1908e659389 100644
--- a/Polyhedron/demo/Polyhedron/Scene_edit_polyhedron_item.cpp
+++ b/Polyhedron/demo/Polyhedron/Scene_edit_polyhedron_item.cpp
@@ -109,6 +109,7 @@ Scene_edit_polyhedron_item::Scene_edit_polyhedron_item
 
 Scene_edit_polyhedron_item::~Scene_edit_polyhedron_item()
 {
+    setVisible(false);
   while(is_there_any_ctrl_vertices_group())
   {
     delete_ctrl_vertices_group(false);