diff --git a/Octree/include/CGAL/Octree.h b/Octree/include/CGAL/Octree.h
index 72e16d79cca..4bf02272394 100644
--- a/Octree/include/CGAL/Octree.h
+++ b/Octree/include/CGAL/Octree.h
@@ -173,7 +173,7 @@ namespace CGAL {
         m_root.unsplit();
       }
 
-      void refine(std::function<bool(const Node &)> split_criterion) {
+      void refine(const std::function<bool(const Node &)> &split_criterion) {
 
         // create a side length map
         for (int i = 0; i <= (int) 10; i++)