diff --git a/GraphicsView/demo/Triangulation_2/Delaunay_triangulation_2.cpp b/GraphicsView/demo/Triangulation_2/Delaunay_triangulation_2.cpp
index 6fa18b9e644..d4fee1bea72 100644
--- a/GraphicsView/demo/Triangulation_2/Delaunay_triangulation_2.cpp
+++ b/GraphicsView/demo/Triangulation_2/Delaunay_triangulation_2.cpp
@@ -21,6 +21,9 @@
 #include <CGAL/Qt/GraphicsViewPolylineInput.h>
 #include <CGAL/Qt/TriangulationGraphicsItem.h>
 #include <CGAL/Qt/VoronoiGraphicsItem.h>
+
+// for viewportsBbox
+#include <CGAL/Qt/utility.h>
   
 // the two base classes
 #include "ui_Delaunay_triangulation_2.h"