diff --git a/libcxx/include/cuchar b/libcxx/include/cuchar
--- a/libcxx/include/cuchar
+++ b/libcxx/include/cuchar
@@ -49,6 +49,10 @@
           not be the case.
 #endif
 
+#if !defined(_LIBCPP_CXX03_LANG)
+#  include <__mbstate_t.h>  // provides ::mbstate_t
+#endif
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
@@ -57,7 +61,6 @@
 
 #if !defined(_LIBCPP_CXX03_LANG)
 
-using ::mbstate_t _LIBCPP_USING_IF_EXISTS;
 using ::size_t _LIBCPP_USING_IF_EXISTS;
 
 #  if !defined(_LIBCPP_HAS_NO_C8RTOMB_MBRTOC8)