diff --git a/GraphicsView/demo/Alpha_shapes_3/MainWindow.ui b/GraphicsView/demo/Alpha_shapes_3/MainWindow.ui
index 7827c0917f6..060780b3650 100644
--- a/GraphicsView/demo/Alpha_shapes_3/MainWindow.ui
+++ b/GraphicsView/demo/Alpha_shapes_3/MainWindow.ui
@@ -106,7 +106,7 @@
  <customwidgets>
   <customwidget>
    <class>Viewer</class>
-   <extends>QWidget</extends>
+   <extends>QGLViewer</extends>
    <header>Viewer.h</header>
   </customwidget>
  </customwidgets>