diff --git a/Interval_support/include/CGAL/Interval_traits.h b/Interval_support/include/CGAL/Interval_traits.h
index 654ed8b51a3..6d434bc477d 100644
--- a/Interval_support/include/CGAL/Interval_traits.h
+++ b/Interval_support/include/CGAL/Interval_traits.h
@@ -52,6 +52,8 @@
 #define CGAL_INTERVAL_TRAITS_H
 
 #include <CGAL/basic.h>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/utility/enable_if.hpp>
 
 namespace CGAL {
 
@@ -192,16 +194,27 @@ proper_subset(Interval interval1, Interval interval2) {
 
 
 // Set operations, functions returing Interval
+//the enable_if is need for MSVC as it is not able to eliminate
+//the function if Interval_traits<Interval>::Intersection has no result_type
+//(like Null_functor)
 template<typename Interval> inline 
 typename Interval_traits<Interval>::Intersection::result_type
-intersection(Interval interval1, Interval interval2) {
+intersection(Interval interval1, Interval interval2, typename boost::enable_if<
+                                                       boost::is_same<
+                                                          typename Interval_traits<Interval>::Is_interval,
+                                                          Tag_true > >::type* = NULL
+) {
     typename Interval_traits<Interval>::Intersection intersection;
     return intersection(interval1, interval2);
 }
 
 template<typename Interval> inline 
 typename Interval_traits<Interval>::Hull::result_type
-hull(Interval interval1, Interval interval2) {
+hull(Interval interval1, Interval interval2, typename boost::enable_if<
+                                                       boost::is_same<
+                                                          typename Interval_traits<Interval>::Is_interval,
+                                                          Tag_true > >::type* = NULL) 
+{
     typename Interval_traits<Interval>::Hull hull;
     return hull(interval1, interval2);
 }
diff --git a/STL_Extension/include/CGAL/tags.h b/STL_Extension/include/CGAL/tags.h
index 423fd26ae4b..79ac1f43a88 100644
--- a/STL_Extension/include/CGAL/tags.h
+++ b/STL_Extension/include/CGAL/tags.h
@@ -50,10 +50,13 @@ inline bool check_tag( Tag_false) {return false;}
 struct Null_tag {};
 
 struct Null_functor {
-  #if defined(BOOST_MSVC) //temporary fix for VC
-  typedef Null_tag result_type;
-  typedef Null_tag second_argument_type; 
-  #endif
+//SL: I commented the following because I fixed
+//in Interval_traits.h the global functions intersection and hull 
+//to check that the type is really an interval
+//  #if defined(BOOST_MSVC) //temporary fix for VC
+//  typedef Null_tag result_type;
+//  typedef Null_tag second_argument_type; 
+//  #endif
 };