Index: libcxx/include/__config
===================================================================
--- libcxx/include/__config
+++ libcxx/include/__config
@@ -822,7 +822,7 @@
 typedef unsigned int   char32_t;
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 
-#ifndef __SIZEOF_INT128__
+#if !defined(__SIZEOF_INT128__) || defined(_MSC_VER)
 #define _LIBCPP_HAS_NO_INT128
 #endif