diff --git a/Polyhedron/examples/Polyhedron/polyhedron_prog_vertex_normal.cpp b/Polyhedron/examples/Polyhedron/polyhedron_prog_vertex_normal.cpp
index 4be9db6c545..f39c08ed009 100644
--- a/Polyhedron/examples/Polyhedron/polyhedron_prog_vertex_normal.cpp
+++ b/Polyhedron/examples/Polyhedron/polyhedron_prog_vertex_normal.cpp
@@ -50,7 +50,12 @@ class My_vertex : public CGAL::HalfedgeDS_vertex_base<Refs, T, P> {
     Norm  norm;
 public:
     My_vertex() {} // repeat mandatory constructors
-    My_vertex( const P& pt) : CGAL::HalfedgeDS_vertex_base<Refs, T, P>(pt) {}
+    My_vertex( const P& pt)
+      : CGAL::HalfedgeDS_vertex_base<Refs, T, P>(pt)
+    {
+      //initialization of the normal
+      norm= CGAL::NULL_VECTOR;
+    }
     typedef Norm Normal_3;
     Normal_3&       normal()       { return norm; }
     const Normal_3& normal() const { return norm; }