diff --git a/include/boost/detail/type_traits.hpp b/include/boost/detail/type_traits.hpp
index 9b45ca2..3f077d2 100644
--- a/include/boost/detail/type_traits.hpp
+++ b/include/boost/detail/type_traits.hpp
@@ -465,8 +465,9 @@ template <typename T, std::size_t sz> struct is_POD<T[sz]>
 //
 // is one type convertable to another?
 template <class From, class To>
-class is_convertible
+struct is_convertible
 {
+private:
  typedef char (&no)[1];
  typedef char (&yes)[2];
 #  if defined(__BORLANDC__) || defined(__GNUC__)
@@ -643,3 +644,4 @@ public:
 
 
 
+