diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/stitch_borders.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/stitch_borders.h
index 25d88759ba5..0d03c4b0cd2 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/stitch_borders.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/stitch_borders.h
@@ -307,7 +307,7 @@ void run_stitch_borders(PM& pmesh,
   CGAL_USE(vpm);
 
   std::vector<vertex_descriptor> vertices_to_delete;
-  for(const halfedges_pair hk : to_stitch)
+  for(const halfedges_pair& hk : to_stitch)
   {
     halfedge_descriptor h1 = hk.first;
     halfedge_descriptor h2 = hk.second;
@@ -367,7 +367,7 @@ void run_stitch_borders(PM& pmesh,
   /// In order to avoid having to maintain a set with halfedges to stitch
   /// we do on purpose next-prev linking that might not be useful but that
   /// is harmless and still less expensive than doing queries in a set
-  for(const halfedges_pair hk : to_stitch)
+  for(const halfedges_pair& hk : to_stitch)
   {
     halfedge_descriptor h1 = hk.first;
     halfedge_descriptor h2 = hk.second;
@@ -385,7 +385,7 @@ void run_stitch_borders(PM& pmesh,
 
   /// update HDS connectivity, removing the second halfedge
   /// of each the pair and its opposite
-  for(const halfedges_pair hk : to_stitch)
+  for(const halfedges_pair& hk : to_stitch)
   {
     halfedge_descriptor h1 = hk.first;
     halfedge_descriptor h2 = hk.second;
@@ -446,7 +446,7 @@ std::size_t stitch_borders_impl(PM& pmesh,
   typedef boost::unordered_map<vertex_descriptor, typename Uf_vertices::handle> Uf_handles;
   Uf_handles uf_handles;
 
-  for(const halfedges_pair hk : to_stitch)
+  for(const halfedges_pair& hk : to_stitch)
   {
     halfedge_descriptor h1 = hk.first;
     halfedge_descriptor h2 = hk.second;
@@ -530,7 +530,7 @@ std::size_t stitch_borders_impl(PM& pmesh,
   {
     std::vector<halfedges_pair> to_stitch_filtered;
     to_stitch_filtered.reserve( to_stitch.size());
-    for(const halfedges_pair hk : to_stitch)
+    for(const halfedges_pair& hk : to_stitch)
     {
       // We test both halfedges because the previous test
       // might involve only one of the two halfedges
@@ -546,7 +546,7 @@ std::size_t stitch_borders_impl(PM& pmesh,
     // redo union find as some "master" vertex might be unstitchable
     uf_vertices.clear();
     uf_handles.clear();
-    for(const halfedges_pair hk : to_stitch_filtered)
+    for(const halfedges_pair& hk : to_stitch_filtered)
     {
       halfedge_descriptor h1 = hk.first;
       halfedge_descriptor h2 = hk.second;