diff --git a/STL_Extension/include/CGAL/type_traits.h b/STL_Extension/include/CGAL/type_traits.h
index c68386c7f76..f64e7c0c57f 100644
--- a/STL_Extension/include/CGAL/type_traits.h
+++ b/STL_Extension/include/CGAL/type_traits.h
@@ -29,6 +29,12 @@ struct is_same_or_derived :
 
 namespace cpp20 {
 
+  template<class T>
+  struct type_identity { using type = T; };
+
+  template<class T>
+  using type_identity_t = typename type_identity<T>::type;
+
   template< class T >
   struct remove_cvref {
       typedef std::remove_cv_t<std::remove_reference_t<T>> type;
@@ -39,6 +45,26 @@ namespace cpp20 {
 
 } // end namespace cpp20
 
+namespace details {
+  template <typename From, typename To, typename = void>
+  struct is_convertible_without_narrowing : std::false_type
+  {};
+
+  template <typename From, typename To>
+  struct is_convertible_without_narrowing<From,
+                                          To,
+                                          std::void_t<decltype(cpp20::type_identity_t<To[]>{std::declval<From>()})>>
+      : std::is_convertible<From, To>
+  {};
+}
+
+template <typename From, typename To>
+struct is_convertible_without_narrowing : details::is_convertible_without_narrowing<From, To>
+{};
+
+template <typename From, typename To>
+inline constexpr bool is_convertible_without_narrowing_v = is_convertible_without_narrowing<From, To>::value;
+
 } // end namespace CGAL
 
 #endif // CGAL_TYPE_TRAITS_H
diff --git a/STL_Extension/test/STL_Extension/test_type_traits.cpp b/STL_Extension/test/STL_Extension/test_type_traits.cpp
index 77586b50c89..caa0e3afa36 100644
--- a/STL_Extension/test/STL_Extension/test_type_traits.cpp
+++ b/STL_Extension/test/STL_Extension/test_type_traits.cpp
@@ -18,14 +18,22 @@ struct B : public A {};
 typedef A C;
 
 int main() {
-  assert( ( ::CGAL::is_same_or_derived< A,A >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< A,B >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< B,A >::value == 0 ) );
-  assert( ( ::CGAL::is_same_or_derived< B,B >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< A,C >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< B,C >::value == 0 ) );
-  assert( ( ::CGAL::is_same_or_derived< C,C >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< C,A >::value == 1 ) );
-  assert( ( ::CGAL::is_same_or_derived< C,B >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< A,A >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< A,B >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< B,A >::value == 0 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< B,B >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< A,C >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< B,C >::value == 0 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< C,C >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< C,A >::value == 1 ) );
+  static_assert( ( ::CGAL::is_same_or_derived< C,B >::value == 1 ) );
+
+  static_assert(   CGAL::is_convertible_without_narrowing_v<int, int> );
+  static_assert( ! CGAL::is_convertible_without_narrowing_v<int, signed char> );
+  static_assert(   CGAL::is_convertible_without_narrowing_v<signed char, int> );
+  static_assert( ! CGAL::is_convertible_without_narrowing_v<int, double> );
+  static_assert(   CGAL::is_convertible_without_narrowing_v<float, double> );
+  static_assert( ! CGAL::is_convertible_without_narrowing_v<double, float> );
+  static_assert( ! CGAL::is_convertible_without_narrowing_v<A, int> );
   return 0;
 }