Index: libcxx/trunk/src/support/win32/locale_win32.cpp
===================================================================
--- libcxx/trunk/src/support/win32/locale_win32.cpp
+++ libcxx/trunk/src/support/win32/locale_win32.cpp
@@ -87,10 +87,16 @@
 
 int snprintf_l(char *ret, size_t n, locale_t loc, const char *format, ...)
 {
+#if !defined(_LIBCPP_MSVCRT)
     __libcpp_locale_guard __current(loc);
+#endif
     va_list ap;
     va_start( ap, format );
+#if defined(_LIBCPP_MSVCRT)
+    int result = _vsnprintf_l( ret, n, format, loc, ap );
+#else
     int result = vsnprintf( ret, n, format, ap );
+#endif
     va_end(ap);
     return result;
 }