diff --git a/AABB_tree/demo/AABB_tree/MainWindow.cpp b/AABB_tree/demo/AABB_tree/MainWindow.cpp
index c5d00c638bb..78a8336f076 100644
--- a/AABB_tree/demo/AABB_tree/MainWindow.cpp
+++ b/AABB_tree/demo/AABB_tree/MainWindow.cpp
@@ -45,6 +45,7 @@ MainWindow::MainWindow(QWidget* parent)
 
 MainWindow::~MainWindow()
 {
+  m_pViewer->makeCurrent();
   delete ui;
 }
 
diff --git a/GraphicsView/include/CGAL/Qt/qglviewer_impl.h b/GraphicsView/include/CGAL/Qt/qglviewer_impl.h
index b097030d1ea..5e6ab9dae8a 100644
--- a/GraphicsView/include/CGAL/Qt/qglviewer_impl.h
+++ b/GraphicsView/include/CGAL/Qt/qglviewer_impl.h
@@ -216,16 +216,6 @@ void CGAL::QGLViewer::initializeGL() {
          || QCoreApplication::arguments().contains(QStringLiteral("--old")))
 
     {
-      format.setDepthBufferSize(24);
-      format.setStencilBufferSize(8);
-      format.setVersion(2,0);
-      format.setRenderableType(QSurfaceFormat::OpenGLES);
-      format.setSamples(0);
-      format.setOption(QSurfaceFormat::DebugContext);
-      QSurfaceFormat::setDefaultFormat(format);
-
-      needNewContext();
-      qDebug()<<"GL 4.3 context initialization failed. ";
       is_ogl_4_3 = false;
     }
     else
diff --git a/Principal_component_analysis/demo/Principal_component_analysis/MainWindow.cpp b/Principal_component_analysis/demo/Principal_component_analysis/MainWindow.cpp
index 0676b175517..13dde23e2a2 100644
--- a/Principal_component_analysis/demo/Principal_component_analysis/MainWindow.cpp
+++ b/Principal_component_analysis/demo/Principal_component_analysis/MainWindow.cpp
@@ -48,6 +48,7 @@ MainWindow::MainWindow(QWidget* parent)
 
 MainWindow::~MainWindow()
 {
+        m_pViewer->makeCurrent();
         delete ui;
 }
 
diff --git a/Principal_component_analysis/demo/Principal_component_analysis/Scene.cpp b/Principal_component_analysis/demo/Principal_component_analysis/Scene.cpp
index e75392cb62d..a4c60dd0a54 100644
--- a/Principal_component_analysis/demo/Principal_component_analysis/Scene.cpp
+++ b/Principal_component_analysis/demo/Principal_component_analysis/Scene.cpp
@@ -28,6 +28,7 @@ Scene::Scene()
 
 Scene::~Scene()
 {
+
     delete m_pPolyhedron;
 }