diff --git a/Polyhedron/demo/Polyhedron/MainWindow.h b/Polyhedron/demo/Polyhedron/MainWindow.h
index ea43c7a482f..b58fa02912f 100644
--- a/Polyhedron/demo/Polyhedron/MainWindow.h
+++ b/Polyhedron/demo/Polyhedron/MainWindow.h
@@ -9,6 +9,7 @@
 #include <QOpenGLWidget>
 #include <CGAL/Qt/DemosMainWindow.h>
 #include <CGAL/Three/Three.h>
+#include <CGAL/Three/Scene_item.h>
 
 #include <QJSEngine>