diff --git a/include/boost/config/compiler/visualc.hpp b/include/boost/config/compiler/visualc.hpp
index fc422ade..5c52c766 100644
--- a/include/boost/config/compiler/visualc.hpp
+++ b/include/boost/config/compiler/visualc.hpp
@@ -205,8 +205,8 @@
 #if (_MSC_VER < 1911) || (_MSVC_LANG < 201703)
 #  define BOOST_NO_CXX17_STRUCTURED_BINDINGS
 #  define BOOST_NO_CXX17_IF_CONSTEXPR
-#  define BOOST_NO_CXX17_HDR_OPTIONAL
-#  define BOOST_NO_CXX17_HDR_STRING_VIEW
+//#  define BOOST_NO_CXX17_HDR_OPTIONAL
+//#  define BOOST_NO_CXX17_HDR_STRING_VIEW
 #endif
 
 // MSVC including version 14 has not yet completely
diff --git a/include/boost/config/stdlib/dinkumware.hpp b/include/boost/config/stdlib/dinkumware.hpp
index e829f08e..420c574b 100644
--- a/include/boost/config/stdlib/dinkumware.hpp
+++ b/include/boost/config/stdlib/dinkumware.hpp
@@ -174,6 +174,8 @@
 #if !defined(_CPPLIB_VER) || (_CPPLIB_VER < 650) || !defined(BOOST_MSVC) || (BOOST_MSVC < 1910) || !defined(_HAS_CXX17) || (_HAS_CXX17 == 0)
 #  define BOOST_NO_CXX17_STD_APPLY
 #  define BOOST_NO_CXX17_ITERATOR_TRAITS
+#  define BOOST_NO_CXX17_HDR_STRING_VIEW
+#  define BOOST_NO_CXX17_HDR_OPTIONAL
 #endif
 #if !defined(_CPPLIB_VER) || (_CPPLIB_VER < 650) || !defined(_HAS_CXX17) || (_HAS_CXX17 == 0) || !defined(_MSVC_STL_UPDATE) || (_MSVC_STL_UPDATE < 201709)
 #  define BOOST_NO_CXX17_STD_INVOKE