diff --git a/include/boost/config/compiler/visualc.hpp b/include/boost/config/compiler/visualc.hpp
index 7612b47e..4859c7c8 100644
--- a/include/boost/config/compiler/visualc.hpp
+++ b/include/boost/config/compiler/visualc.hpp
@@ -236,7 +236,9 @@
 // if this is in effect or not, in any case nothing in Boost is currently using this, so we'll just go
 // on defining it for now:
 //
+#if (_MSC_FULL_VER < 193030705)  || (_MSVC_LANG < 202004)
 #  define BOOST_NO_TWO_PHASE_NAME_LOOKUP
+#endif
 
 #if (_MSC_VER < 1912) || (_MSVC_LANG < 201402)
 // Supported from msvc-15.5 onwards:
diff --git a/include/boost/config/stdlib/dinkumware.hpp b/include/boost/config/stdlib/dinkumware.hpp
index b1d97f1b..a9d3706c 100644
--- a/include/boost/config/stdlib/dinkumware.hpp
+++ b/include/boost/config/stdlib/dinkumware.hpp
@@ -209,8 +209,10 @@
 #endif
 // C++20 features not yet implemented:
 #  define BOOST_NO_CXX20_HDR_FORMAT
+#if !defined(_MSVC_STL_UPDATE) || (_MSVC_STL_UPDATE < 202108L) || !defined(_HAS_CXX20) || (_HAS_CXX20 == 0)
 #  define BOOST_NO_CXX20_HDR_SOURCE_LOCATION
 #  define BOOST_NO_CXX20_HDR_SYNCSTREAM
+#endif
 // Incomplete:
 #  define BOOST_NO_CXX20_HDR_RANGES