diff --git a/Nef_3/include/CGAL/Nef_3/ID_support_handler.h b/Nef_3/include/CGAL/Nef_3/ID_support_handler.h
index a6dd108b221..13235bc9415 100644
--- a/Nef_3/include/CGAL/Nef_3/ID_support_handler.h
+++ b/Nef_3/include/CGAL/Nef_3/ID_support_handler.h
@@ -65,16 +65,18 @@ class ID_support_handler<SNC_indexed_items, Decorator> {
     hash.reserve(n);
   }
 
-  // The method get_hash implements a
-  // two-pass union find algorithm
-  //    __    __           _______
-  //   /  \  /  \         /  _____\
-  //  _|__|__|__|_      _/__/__/__|_
-  // | |  v  |  v |    | |  |  |  v |
-  // | O  O  O  O | => | O  O  O  O |
-  // |____|__^____|    |____________|
-  //      |  | root
-  //      \_/
+  /*
+     The method get_hash implements a
+     two-pass union find algorithm
+        __    __           _______
+       /  \  /  \         /  _____\
+      _|__|__|__|_      _/__/__/__|_
+     | |  v  |  v |    | |  |  |  v |
+     | O  O  O  O | => | O  O  O  O |
+     |____|__^____|    |____________|
+          |  | root
+          \_/
+  */
   int get_hash(int i) {
     int root(i);
     while(hash[root] != root)
diff --git a/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h b/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h
index 9a9b3bcfcd1..c8523a2ee7d 100644
--- a/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h
+++ b/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h
@@ -38,6 +38,8 @@ class ID_support_handler {
  public:
   ID_support_handler() {}
 
+  void reserve(std::size_t n) {}
+
   int get_hash(int) { return 0; }
   template<typename Handle> void initialize_hash(Handle /*h*/) {}
   void initialize_hash(int /*i*/) {}