diff --git a/include/boost/config/detail/suffix.hpp b/include/boost/config/detail/suffix.hpp
index 169683c9..28854e5e 100644
--- a/include/boost/config/detail/suffix.hpp
+++ b/include/boost/config/detail/suffix.hpp
@@ -1124,7 +1124,7 @@ namespace std{ using ::type_info; }
 #endif
 
 #if !defined(_YVALS) && !defined(_CPPLIB_VER)  // msvc std lib already configured
-#if (!defined(__has_include) || (__cplusplus < 201703))
+#if (!defined(__has_include) || (__cplusplus < 201704))
 #  define BOOST_NO_CXX20_HDR_BARRIER
 #  define BOOST_NO_CXX20_HDR_FORMAT
 #  define BOOST_NO_CXX20_HDR_SOURCE_LOCATION
diff --git a/include/boost/config/stdlib/dinkumware.hpp b/include/boost/config/stdlib/dinkumware.hpp
index 78bf3605..fb584205 100644
--- a/include/boost/config/stdlib/dinkumware.hpp
+++ b/include/boost/config/stdlib/dinkumware.hpp
@@ -193,7 +193,7 @@
 #endif
 
 // C++20 features
-#if !defined(_MSVC_STL_UPDATE) || (_MSVC_STL_UPDATE < 202008L)
+#if !defined(_MSVC_STL_UPDATE) || (_MSVC_STL_UPDATE < 202008L) || !defined(_HAS_CXX20) || (_HAS_CXX20 == 0)
 #  define BOOST_NO_CXX20_HDR_BARRIER
 #  define BOOST_NO_CXX20_HDR_BIT
 #  define BOOST_NO_CXX20_HDR_LATCH