diff --git a/Nef_3/include/CGAL/boost/graph/convert_nef_polyhedron_to_polygon_mesh.h b/Nef_3/include/CGAL/boost/graph/convert_nef_polyhedron_to_polygon_mesh.h
index c055798f877..218e7210866 100644
--- a/Nef_3/include/CGAL/boost/graph/convert_nef_polyhedron_to_polygon_mesh.h
+++ b/Nef_3/include/CGAL/boost/graph/convert_nef_polyhedron_to_polygon_mesh.h
@@ -363,12 +363,82 @@ void convert_nef_polyhedron_to_polygon_soup(const Nef_polyhedron& nef,
 
   auto shell_is_closed = [](typename Nef_polyhedron::Shell_entry_const_iterator sfh)
   {
-    typename Nef_polyhedron::Halffacet_const_handle f;
+    typename Nef_polyhedron::SFace_const_handle sf = sfh;
 
-    if (CGAL::assign(f,*sfh))
-      return f->incident_volume()!=f->twin()->incident_volume();
-    else
-      return false;
+    typename Nef_polyhedron::SFace_cycle_const_iterator fc;
+    for(fc = sf->sface_cycles_begin(); fc != sf->sface_cycles_end(); ++fc)
+    {
+      if (fc.is_shalfedge() ) {
+        typename Nef_polyhedron::SHalfedge_const_handle e(fc);
+        typename Nef_polyhedron::SHalfedge_around_sface_const_circulator ec(e),ee(e);
+        CGAL_For_all(ec,ee)
+        {
+          typename Nef_polyhedron::SVertex_const_handle vv = ec->twin()->source();
+          //~ if ( !SD.is_isolated(vv) && !Done[vv] ) {
+            //~ V.visit(vv); // report edge
+            //~ Done[vv] = Done[vv->twin()] = true;
+          //~ }
+          typename Nef_polyhedron::Halffacet_const_handle f = ec->twin()->facet();
+          return f->incident_volume()!=f->twin()->incident_volume();
+          //~ if ( Done[f] ) continue;
+          //~ Halffacet_handle tf = f->twin();
+          //~ }
+          //~ FacetCandidates.push_back(f); Done[f] = true;
+        }
+      }
+
+#if 0
+      else if (fc.is_svertex() ) {
+        SVertex_handle v(fc);
+        if ( Done[v] ) continue;
+        V.visit(v); // report edge
+        V.visit(v->twin());
+        Done[v] = Done[v->twin()] = true;
+        CGAL_assertion(SD.is_isolated(v));
+        SFaceCandidates.push_back(v->twin()->incident_sface());
+        Done[v->twin()->incident_sface()]=true;
+        // note that v is isolated, thus twin(v) is isolated too
+        //          SM_const_decorator SD;
+        //          SFace_const_handle fo;
+        //          fo = v->twin()->incident_sface();
+        /*
+        if(SD.is_isolated(v))
+          fo = v->source()->sfaces_begin();
+        else
+          fo = v->twin()->incident_sface();
+        */
+      } else if (fc.is_shalfloop() ) {
+        SHalfloop_handle l(fc);
+        V.visit(l);
+        Halffacet_handle f = l->twin()->facet();
+        if ( Done[f] ) continue;
+        FacetCandidates.push_back(f);  Done[f] = true;
+      } else CGAL_error_msg("Damn wrong handle.");
+#endif
+    }
+
+    return false;
+
+    //~ typename Nef_polyhedron::SHalfedge_const_handle e(sf);
+    //~ typename Nef_polyhedron::SHalffacet_const_handle f = e->facet();
+  //~ e->facet()
+  //~ SHalfedge_around_sface_circulator ec(e),ee(e);
+  //~ CGAL_For_all(ec,ee) {
+          //~ SVertex_handle vv = ec->twin()->source();
+          //~ if ( !SD.is_isolated(vv) && !Done[vv] ) {
+            //~ V.visit(vv); // report edge
+            //~ Done[vv] = Done[vv->twin()] = true;
+          //~ }
+          //~ Halffacet_handle f = ec->twin()->facet();
+          //~ if ( Done[f] ) continue;
+
+  //~ if (CGAL::assign(f,*sfh))
+  //~ {
+    //~ std::cout << "COUCOU\n";
+      //~ return f->incident_volume()!=f->twin()->incident_volume();
+    //~ }
+    //~ else
+      //~ return false;
   };
 
   for (;vol_it!=vol_end;++vol_it)