#ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
# include <boost/type_traits/remove_reference.hpp>
-#else
-# include <boost/type_traits/add_reference.hpp>
-#endif
+#endif
+#include <boost/type_traits/add_reference.hpp>
#include <boost/iterator/detail/config_def.hpp>
#include <boost/iterator/iterator_traits.hpp>