diff --git a/include/boost/detail/iterator.hpp b/include/boost/detail/iterator.hpp
index d97bfd7..158bcd1 100644
--- a/include/boost/detail/iterator.hpp
+++ b/include/boost/detail/iterator.hpp
@@ -348,7 +348,6 @@ template <> struct iterator_traits_select<false>
 #   elif !defined(BOOST_BAD_OUTPUT_ITERATOR_SPECIALIZATION)
         typedef typename Iterator::difference_type difference_type;
         typedef typename Iterator::value_type value_type;
-        typedef typename Iterator::difference_type difference_type;
         typedef typename Iterator::pointer pointer;
         typedef typename Iterator::reference reference;
 #   else