--- sp_has_sync.bak	2017-07-11 16:37:21.840678200 +0000
+++ sp_has_sync.hpp	2017-07-11 16:37:58.779891600 +0000
@@ -46,4 +46,6 @@
 
 #endif // __GNUC__ * 100 + __GNUC_MINOR__ >= 401
 
+#undef BOOST_SP_HAS_SYNC
+
 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SP_HAS_SYNC_HPP_INCLUDED