diff --git a/Installation/include/CGAL/config.h b/Installation/include/CGAL/config.h
index 8206195e6b2..432229f8e2d 100644
--- a/Installation/include/CGAL/config.h
+++ b/Installation/include/CGAL/config.h
@@ -354,13 +354,6 @@ using std::max;
 #  define CGAL_UNUSED
 #endif
 
-// Macro to specify that gcc's pedantic mode should not warn.
-#ifdef __GNUG__
-#  define CGAL_GNU_EXTENSION  __extension__
-#else
-#  define CGAL_GNU_EXTENSION
-#endif
-
 // Macro CGAL_ASSUME
 // Call a builtin of the compiler to pass a hint to the compiler
 #if __has_builtin(__builtin_unreachable) || (CGAL_GCC_VERSION >= 40500 && !__STRICT_ANSI__)
diff --git a/Number_types/include/CGAL/long_long.h b/Number_types/include/CGAL/long_long.h
index ea98538a058..18fd669d80e 100644
--- a/Number_types/include/CGAL/long_long.h
+++ b/Number_types/include/CGAL/long_long.h
@@ -90,9 +90,8 @@ template <> class Real_embeddable_traits< unsigned long long >
 
 #ifdef BOOST_HAS_INT128
 // __int128
-CGAL_GNU_EXTENSION
-template<> class Algebraic_structure_traits< __int128 >
-  : public Algebraic_structure_traits_base< __int128,
+template<> class Algebraic_structure_traits< boost::int128_type >
+  : public Algebraic_structure_traits_base< boost::int128_type,
                                             Euclidean_ring_tag > {
 
   public:
@@ -104,9 +103,8 @@ template<> class Algebraic_structure_traits< __int128 >
 
 };
 
-CGAL_GNU_EXTENSION
-template <> class Real_embeddable_traits< __int128 >
-  : public INTERN_RET::Real_embeddable_traits_base< __int128 , CGAL::Tag_true > {
+template <> class Real_embeddable_traits< boost::int128_type >
+  : public INTERN_RET::Real_embeddable_traits_base< boost::int128_type , CGAL::Tag_true > {
   public:
 
     class To_interval
@@ -119,9 +117,8 @@ template <> class Real_embeddable_traits< __int128 >
 };
 
 // unsigned __int128
-CGAL_GNU_EXTENSION
-template <> class Real_embeddable_traits< unsigned __int128 >
-  : public INTERN_RET::Real_embeddable_traits_base< unsigned __int128 , CGAL::Tag_true > {
+template <> class Real_embeddable_traits< boost::uint128_type >
+  : public INTERN_RET::Real_embeddable_traits_base< boost::uint128_type , CGAL::Tag_true > {
   public:
 
     class To_interval