diff --git a/Voronoi_diagram_2/demo/Voronoi_diagram_2/my_window.h b/Voronoi_diagram_2/demo/Voronoi_diagram_2/my_window.h
index 6e4dd693311..8e9940ec2ff 100644
--- a/Voronoi_diagram_2/demo/Voronoi_diagram_2/my_window.h
+++ b/Voronoi_diagram_2/demo/Voronoi_diagram_2/my_window.h
@@ -462,7 +462,7 @@ private slots:
     CGAL::Timer timer;
     vvd->clear();
 
-    std::ifstream f(fileName);
+    std::ifstream f(fileName.ascii());
     assert( f );
 
     int counter = 0;