diff --git a/Envelope_3/include/CGAL/Env_plane_traits_3.h b/Envelope_3/include/CGAL/Env_plane_traits_3.h
index acf2780e183..f5e616ccb34 100644
--- a/Envelope_3/include/CGAL/Env_plane_traits_3.h
+++ b/Envelope_3/include/CGAL/Env_plane_traits_3.h
@@ -54,10 +54,10 @@ class Env_plane_traits_3 : public Arr_linear_traits_2<Kernel_>
   typedef typename Kernel::Object_3            Object_3;
   typedef std::pair<Curve_2, Multiplicity>     Intersection_curve;
 
-  typedef Arr_open_side_tag                    Arr_left_side_tag;
-  typedef Arr_open_side_tag                    Arr_bottom_side_tag;
-  typedef Arr_open_side_tag                    Arr_top_side_tag;
-  typedef Arr_open_side_tag                    Arr_righ_side_tag;
+  typedef Base::Arr_left_side_tag              Arr_left_side_tag;
+  typedef Base::Arr_bottom_side_tag            Arr_bottom_side_tag;
+  typedef Base::Arr_top_side_tag               Arr_top_side_tag;
+  typedef Base::Arr_right_side_tag             Arr_righ_side_tag;
   
   class Is_vertical_3
   {