diff --git a/Polyhedron/demo/Polyhedron/MainWindow.ui b/Polyhedron/demo/Polyhedron/MainWindow.ui
index 07173c3fa40..b0b4d2c94ad 100644
--- a/Polyhedron/demo/Polyhedron/MainWindow.ui
+++ b/Polyhedron/demo/Polyhedron/MainWindow.ui
@@ -332,7 +332,7 @@
  <customwidgets>
   <customwidget>
    <class>Viewer</class>
-   <extends>QWidget</extends>
+   <extends>QGLViewer</extends>
    <header>Viewer.h</header>
   </customwidget>
  </customwidgets>