diff --git a/libcxx/include/__bsd_locale_fallbacks.h b/libcxx/include/__bsd_locale_fallbacks.h
--- a/libcxx/include/__bsd_locale_fallbacks.h
+++ b/libcxx/include/__bsd_locale_fallbacks.h
@@ -23,6 +23,8 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+
 inline _LIBCPP_INLINE_VISIBILITY
 decltype(MB_CUR_MAX) __libcpp_mb_cur_max_l(locale_t __l)
 {
@@ -88,14 +90,14 @@
     __libcpp_locale_guard __current(__l);
     return mbrlen(__s, __n, __ps);
 }
-
+#endif
 inline _LIBCPP_INLINE_VISIBILITY
 lconv *__libcpp_localeconv_l(locale_t __l)
 {
     __libcpp_locale_guard __current(__l);
     return localeconv();
 }
-
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 inline _LIBCPP_INLINE_VISIBILITY
 size_t __libcpp_mbsrtowcs_l(wchar_t *__dest, const char **__src, size_t __len,
                      mbstate_t *__ps, locale_t __l)
@@ -103,7 +105,7 @@
     __libcpp_locale_guard __current(__l);
     return mbsrtowcs(__dest, __src, __len, __ps);
 }
-
+#endif
 inline
 int __libcpp_snprintf_l(char *__s, size_t __n, locale_t __l, const char *__format, ...) {
     va_list __va;
diff --git a/libcxx/include/__mbstate_t.h b/libcxx/include/__mbstate_t.h
--- a/libcxx/include/__mbstate_t.h
+++ b/libcxx/include/__mbstate_t.h
@@ -28,7 +28,7 @@
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 #   include <wchar.h> // for mbstate_t
 #else
-#   include <sys/_types/_mbstate_t.h> // works on Darwin
+#  include <bits/types/mbstate_t.h> // works on Linux
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD