diff --git a/Alpha_shapes_3/demo/Alpha_shapes_3/Viewer.h b/Alpha_shapes_3/demo/Alpha_shapes_3/Viewer.h
index ff19159d837..289ae385c1e 100644
--- a/Alpha_shapes_3/demo/Alpha_shapes_3/Viewer.h
+++ b/Alpha_shapes_3/demo/Alpha_shapes_3/Viewer.h
@@ -21,6 +21,7 @@ public:
   Viewer(QWidget* parent);
   ~Viewer()
   {
+    makeCurrent();
     buffers[0].destroy();
     buffers[1].destroy();
     buffers[2].destroy();
diff --git a/Circular_kernel_3/demo/Circular_kernel_3/Viewer.cpp b/Circular_kernel_3/demo/Circular_kernel_3/Viewer.cpp
index 69901dbbd1c..aa5a06c1354 100644
--- a/Circular_kernel_3/demo/Circular_kernel_3/Viewer.cpp
+++ b/Circular_kernel_3/demo/Circular_kernel_3/Viewer.cpp
@@ -11,6 +11,14 @@ Viewer::Viewer(QWidget* parent )
 {
     extension_is_found = false;
 }
+Viewer::~Viewer()
+{
+  makeCurrent();
+  for(int i=0; i<3; ++i)
+    vao[i].destroy();
+  for(int i=0; i<9; ++i)
+    buffers[i].destroy();
+}
 
 void Viewer::compile_shaders()
 {
diff --git a/Circular_kernel_3/demo/Circular_kernel_3/Viewer.h b/Circular_kernel_3/demo/Circular_kernel_3/Viewer.h
index ea178e756a0..cad037ce2c8 100644
--- a/Circular_kernel_3/demo/Circular_kernel_3/Viewer.h
+++ b/Circular_kernel_3/demo/Circular_kernel_3/Viewer.h
@@ -13,6 +13,7 @@ class Viewer : public CGAL::QGLViewer
 {
 public:
     Viewer(QWidget* parent = 0);
+    ~Viewer();
   GLuint dl_nb;
 protected :
   virtual void draw();
diff --git a/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/Scene.h b/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/Scene.h
index 41d4311ebe8..32f3926c802 100644
--- a/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/Scene.h
+++ b/Periodic_3_triangulation_3/demo/Periodic_3_triangulation_3/Scene.h
@@ -76,6 +76,7 @@ public:
   }
 
   ~Scene() {
+    ui->viewer->makeCurrent();
     for(int i=0; i<24; i++)
         buffers[i].destroy();
     for(int i=0; i<12; i++)
diff --git a/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/Viewer.h b/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/Viewer.h
index 1ea4397cf4c..7ba3534a6d2 100644
--- a/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/Viewer.h
+++ b/Periodic_3_triangulation_3/demo/Periodic_Lloyd_3/Viewer.h
@@ -27,6 +27,7 @@ public:
   {}
   ~Viewer()
   {
+    makeCurrent();
    for(int i=0; i<4; i++)
    {
     buffers[i].destroy();
diff --git a/Polyhedron/demo/Polyhedron/Viewer.cpp b/Polyhedron/demo/Polyhedron/Viewer.cpp
index 95ede4b08db..67106261b3e 100644
--- a/Polyhedron/demo/Polyhedron/Viewer.cpp
+++ b/Polyhedron/demo/Polyhedron/Viewer.cpp
@@ -374,6 +374,7 @@ Viewer::Viewer(QWidget* parent,
 
 Viewer::~Viewer()
 {
+  makeCurrent();
     QSettings viewer_settings;
     viewer_settings.setValue("cam_pos",
                              QString("%1,%2,%3")