diff --git a/Segment_Delaunay_graph_2/include/CGAL/Segment_Delaunay_graph_hierarchy_2.h b/Segment_Delaunay_graph_2/include/CGAL/Segment_Delaunay_graph_hierarchy_2.h
index dfc87716f44..9077dd05292 100644
--- a/Segment_Delaunay_graph_2/include/CGAL/Segment_Delaunay_graph_hierarchy_2.h
+++ b/Segment_Delaunay_graph_2/include/CGAL/Segment_Delaunay_graph_hierarchy_2.h
@@ -406,7 +406,7 @@ public:
   Vertex_handle  nearest_neighbor(const Point_2& p,
 				  bool force_point = false) const;
 
-  Vertex_handle  nearest_neighbor(const Point_2& p, Vertex_handle)
+  Vertex_handle  nearest_neighbor(const Point_2& p, Vertex_handle) const
   {
     return nearest_neighbor(p);
   }