diff --git a/libcxx/include/__cxx03/__config b/libcxx/include/__cxx03/__config
index ef47327d96355..0839d19ad5ab4 100644
--- a/libcxx/include/__cxx03/__config
+++ b/libcxx/include/__cxx03/__config
@@ -595,7 +595,9 @@ typedef __char32_t char32_t;
 // clang-format on
 
 #  if defined(__APPLE__) || defined(__FreeBSD__) || defined(_LIBCPP_MSVCRT_LIKE) || defined(__NetBSD__)
-#    define _LIBCPP_LOCALE__L_EXTENSIONS 1
+#    if !defined(__MSVCRT_VERSION__) || __MSVCRT_VERSION__ >= 0x800
+#      define _LIBCPP_LOCALE__L_EXTENSIONS 1
+#    endif
 #  endif
 
 #  ifdef __FreeBSD__
diff --git a/libcxx/include/__locale_dir/support/windows.h b/libcxx/include/__locale_dir/support/windows.h
index 0d3089c150081..6a2ffd897bb7a 100644
--- a/libcxx/include/__locale_dir/support/windows.h
+++ b/libcxx/include/__locale_dir/support/windows.h
@@ -221,6 +221,23 @@ inline _LIBCPP_HIDE_FROM_ABI size_t __strxfrm(char* __dest, const char* __src, s
 }
 
 #  if _LIBCPP_HAS_WIDE_CHARACTERS
+#    if defined(__MINGW32__) && __MSVCRT_VERSION__ < 0x0800
+_LIBCPP_EXPORTED_FROM_ABI int __iswctype(wint_t c, wctype_t __type, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswspace(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswprint(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswcntrl(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswupper(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswlower(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswalpha(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswblank(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswdigit(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswpunct(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __iswxdigit(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI wint_t __towupper(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI wint_t __towlower(wint_t c, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI int __wcscoll(const wchar_t* ws1, const wchar_t* ws2, __locale_t loc);
+_LIBCPP_EXPORTED_FROM_ABI size_t __wcsxfrm(wchar_t* dest, const wchar_t* src, size_t n, __locale_t loc);
+#    else
 inline _LIBCPP_HIDE_FROM_ABI int __iswctype(wint_t __c, wctype_t __type, __locale_t __loc) {
   return ::_iswctype_l(__c, __type, __loc);
 }
@@ -245,7 +262,8 @@ inline _LIBCPP_HIDE_FROM_ABI int __wcscoll(const wchar_t* __ws1, const wchar_t*
 inline _LIBCPP_HIDE_FROM_ABI size_t __wcsxfrm(wchar_t* __dest, const wchar_t* __src, size_t __n, __locale_t __loc) {
   return ::_wcsxfrm_l(__dest, __src, __n, __loc);
 }
-#  endif // _LIBCPP_HAS_WIDE_CHARACTERS
+#    endif // defined(__MINGW32__) && __MSVCRT_VERSION__ < 0x0800
+#  endif   // _LIBCPP_HAS_WIDE_CHARACTERS
 
 #  if defined(__MINGW32__) && __MSVCRT_VERSION__ < 0x0800
 _LIBCPP_EXPORTED_FROM_ABI size_t __strftime(char*, size_t, const char*, const struct tm*, __locale_t);
diff --git a/libcxx/src/support/win32/locale_win32.cpp b/libcxx/src/support/win32/locale_win32.cpp
index 24402e818d95d..f8a963faa572f 100644
--- a/libcxx/src/support/win32/locale_win32.cpp
+++ b/libcxx/src/support/win32/locale_win32.cpp
@@ -57,6 +57,68 @@ size_t __strftime(char* ret, size_t n, const char* format, const struct tm* tm,
   __locale_guard __current(loc);
   return std::strftime(ret, n, format, tm);
 }
+#  if _LIBCPP_HAS_WIDE_CHARACTERS
+int __iswctype(wint_t c, wctype_t type, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswctype(c, type);
+}
+int __iswspace(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswspace(c);
+}
+int __iswprint(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswprint(c);
+}
+int __iswcntrl(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswcntrl(c);
+}
+int __iswupper(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswupper(c);
+}
+int __iswlower(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswlower(c);
+}
+int __iswalpha(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswalpha(c);
+}
+int __iswblank(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswblank(c);
+}
+int __iswdigit(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswdigit(c);
+}
+int __iswpunct(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswpunct(c);
+}
+int __iswxdigit(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::iswxdigit(c);
+}
+wint_t __towupper(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::towupper(c);
+}
+wint_t __towlower(wint_t c, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::towlower(c);
+}
+int __wcscoll(const wchar_t* ws1, const wchar_t* ws2, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::wcscoll(ws1, ws2);
+}
+size_t __wcsxfrm(wchar_t* dest, const wchar_t* src, size_t n, __locale_t loc) {
+  __locale_guard __current(loc);
+  return ::wcsxfrm(dest, src, n);
+}
+#  endif
 #endif
 
 //