diff --git a/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h b/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
index fb9b023ea62..66c18644bed 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
@@ -498,6 +498,12 @@ namespace CartesianKernelFunctors {
 					       q.x(), q.y(), q.z() ),
 			      ft);
     }
+    
+    result_type
+    operator()(const Point_3&, const FT& ft) const
+    {
+      return - CGAL_NTS sign(ft);
+    }    
   };