diff --git a/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_inserters.h b/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_inserters.h
index 037a3326725..1d59b6e146e 100644
--- a/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_inserters.h
+++ b/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_inserters.h
@@ -124,8 +124,9 @@ private:
 //===========================================================================
 
 template<class AT>
-struct Default_caching_site_inserter<AT,Null_functor>
+class Default_caching_site_inserter<AT,Null_functor>
 {
+public:
   Default_caching_site_inserter() {}
   template<typename T> Default_caching_site_inserter(T t) {}
 };
diff --git a/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_removers.h b/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_removers.h
index 26b84669006..ea815f8e104 100644
--- a/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_removers.h
+++ b/Voronoi_diagram_2/include/CGAL/Voronoi_diagram_2/Default_site_removers.h
@@ -102,8 +102,9 @@ private:
 //===========================================================================
 
 template<class AT>
-struct Default_caching_site_remover<AT,Null_functor>
+class Default_caching_site_remover<AT,Null_functor>
 {
+public:
   Default_caching_site_remover() {}
   template<typename T> Default_caching_site_remover(T t) {}
 };