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 c8523a2ee7d..c9033b607f2 100644
--- a/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h
+++ b/Nef_S2/include/CGAL/Nef_S2/ID_support_handler.h
@@ -38,7 +38,7 @@ class ID_support_handler {
  public:
   ID_support_handler() {}
 
-  void reserve(std::size_t n) {}
+  void reserve(std::size_t) {}
 
   int get_hash(int) { return 0; }
   template<typename Handle> void initialize_hash(Handle /*h*/) {}