diff --git a/src/opengl/qopenglcompositor_p.h b/src/opengl/qopenglcompositor_p.h
index abe8d4959e..66dd77c1c2 100644
--- a/src/opengl/qopenglcompositor_p.h
+++ b/src/opengl/qopenglcompositor_p.h
@@ -29,6 +29,7 @@ class QOpenGLFramebufferObject;
 class QWindow;
 class QPlatformTextureList;
 
+class QOpenGLCompositorBackingStore;
 class QOpenGLCompositorWindow
 {
 public:
@@ -37,6 +38,8 @@ public:
     virtual const QPlatformTextureList *textures() const = 0;
     virtual void beginCompositing() { }
     virtual void endCompositing() { }
+    virtual void setBackingStore(QOpenGLCompositorBackingStore *backingStore) = 0;
+    virtual QOpenGLCompositorBackingStore *backingStore() const = 0;
 };
 
 class Q_OPENGL_EXPORT QOpenGLCompositor : public QObject
diff --git a/src/opengl/qopenglcompositorbackingstore.cpp b/src/opengl/qopenglcompositorbackingstore.cpp
index 8bc1ec75ff..8efccce579 100644
--- a/src/opengl/qopenglcompositorbackingstore.cpp
+++ b/src/opengl/qopenglcompositorbackingstore.cpp
@@ -137,6 +137,9 @@ void QOpenGLCompositorBackingStore::updateTexture()
 void QOpenGLCompositorBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
 {
     // Called for ordinary raster windows.
+    auto *handle = dynamic_cast<QOpenGLCompositorWindow *>(window->handle());
+    if (handle && !handle->backingStore())
+        handle->setBackingStore(this);
 
     Q_UNUSED(region);
     Q_UNUSED(offset);
diff --git a/src/plugins/platforms/eglfs/api/qeglfswindow_p.h b/src/plugins/platforms/eglfs/api/qeglfswindow_p.h
index d111042040..e51cd69f3d 100644
--- a/src/plugins/platforms/eglfs/api/qeglfswindow_p.h
+++ b/src/plugins/platforms/eglfs/api/qeglfswindow_p.h
@@ -70,8 +70,8 @@ public:
     bool isRaster() const;
 
 #ifndef QT_NO_OPENGL
-    QOpenGLCompositorBackingStore *backingStore() { return m_backingStore; }
-    void setBackingStore(QOpenGLCompositorBackingStore *backingStore);
+    QOpenGLCompositorBackingStore *backingStore() const override { return m_backingStore; }
+    void setBackingStore(QOpenGLCompositorBackingStore *backingStore) override;
     QWindow *sourceWindow() const override;
     const QPlatformTextureList *textures() const override;
     void endCompositing() override;