diff --git a/Kernel_23/include/CGAL/Kernel/function_objects.h b/Kernel_23/include/CGAL/Kernel/function_objects.h
index 41e978b703b..21e1db34de4 100644
--- a/Kernel_23/include/CGAL/Kernel/function_objects.h
+++ b/Kernel_23/include/CGAL/Kernel/function_objects.h
@@ -3292,11 +3292,10 @@ namespace CommonKernelFunctors {
     bool operator()(const Sphere_3& s1, const Sphere_3& s2,
                     const Point_3& a, const Point_3& b) const
     {
-      typedef typename K::Circle_3    Circle_3;
-      typedef typename K::Point_3     Point_3;
-      typedef typename K::Segment_3   Segment_3;
-      typedef typename K::Plane_3     Plane_3;
-      typedef typename K::Intersect_3 Intersect_3;
+      typedef typename K::Circle_3  Circle_3;
+      typedef typename K::Point_3   Point_3;
+      typedef typename K::Segment_3 Segment_3;
+      typedef typename K::Plane_3   Plane_3;
 
       const Has_on_bounded_side_3& has_on_bounded_side = *this;
 
diff --git a/STL_Extension/include/CGAL/result_of.h b/STL_Extension/include/CGAL/result_of.h
index 1ed20008f20..863ddb90806 100644
--- a/STL_Extension/include/CGAL/result_of.h
+++ b/STL_Extension/include/CGAL/result_of.h
@@ -21,7 +21,11 @@
 #include <CGAL/config.h>
 #include <CGAL/disable_warnings.h>
 
-#if CGAL_CXX11
+#if CGAL_CXX20 || __cpp_lib_is_invocable>=201703L
+
+  // C++>=17
+
+#elif CGAL_CXX11
 
   #include <type_traits>
 
@@ -45,7 +49,7 @@
 namespace CGAL {
 namespace cpp11 {
 
-#if CGAL_CXX20
+#if CGAL_CXX20 || __cpp_lib_is_invocable>=201703L
 
   template<typename Signature> class result_of;
   template<typename F, typename... Args>
@@ -59,7 +63,7 @@ namespace cpp11 {
 
   using boost::result_of;
 
-#endif
+#endif // end C++<11
 
 } // end cpp11
 } // end CGAL