diff --git a/include/boost/iterator_adaptors.hpp b/include/boost/iterator_adaptors.hpp
index a16b7f0..18e7c9c 100644
--- a/include/boost/iterator_adaptors.hpp
+++ b/include/boost/iterator_adaptors.hpp
@@ -1354,9 +1354,9 @@ namespace detail {
   template <class Base, class T>
   struct reduce_to_base_class
   {
-      BOOST_STATIC_CONSTANT(bool, convertible = (::boost::is_convertible<T*,Base*>::value));
-      typedef typename if_true<convertible
-          >::template then<Base,T>::type type;
+      typedef typename if_true<(
+            ::boost::is_convertible<T*,Base*>::value
+          )>::template then<Base,T>::type type;
   };
 
   // "Steps down" the category of iterators below bidirectional so the category