diff --git a/scene_opengl.h b/scene_opengl.h
--- a/scene_opengl.h
+++ b/scene_opengl.h
@@ -141,9 +141,6 @@
     virtual void updateProjectionMatrix() override;
     void paintCursor() override;
 
-private Q_SLOTS:
-    void resetLanczosFilter();
-
 private:
     void performPaintWindow(EffectWindowImpl* w, int mask, QRegion region, WindowPaintData& data);
     QMatrix4x4 createProjectionMatrix() const;
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -1185,21 +1185,19 @@
     if (mask & PAINT_WINDOW_LANCZOS) {
         if (!m_lanczosFilter) {
             m_lanczosFilter = new LanczosFilter(this);
-            // recreate the lanczos filter when the screen gets resized
-            connect(screens(), SIGNAL(changed()), SLOT(resetLanczosFilter()));
+            // reset the lanczos filter when the screen gets resized
+            // it will get created next paint
+            connect(screens(), &Screens::changed, this, [this]() {
+                makeOpenGLContextCurrent();
+                delete m_lanczosFilter;
+                m_lanczosFilter = NULL;
+            });
         }
         m_lanczosFilter->performPaint(w, mask, region, data);
     } else
         w->sceneWindow()->performPaint(mask, region, data);
 }
 
-void SceneOpenGL2::resetLanczosFilter()
-{
-    // TODO: Qt5 - replace by a lambda slot
-    delete m_lanczosFilter;
-    m_lanczosFilter = NULL;
-}
-
 //****************************************
 // SceneOpenGL::Texture
 //****************************************