diff --git a/include/boost/detail/utf8_codecvt_facet.hpp b/include/boost/detail/utf8_codecvt_facet.hpp
index b777ff9..65c5e4e 100644
--- a/include/boost/detail/utf8_codecvt_facet.hpp
+++ b/include/boost/detail/utf8_codecvt_facet.hpp
@@ -92,7 +92,8 @@ namespace std {
 }
 #endif
 
-#if !defined(__MSL_CPP__) && !defined(__LIBCOMO__)
+#if !defined(__MSL_CPP__) && !defined(__LIBCOMO__) \
+    && !defined(_LIBCPP_VERSION)
     #define BOOST_CODECVT_DO_LENGTH_CONST const
 #else
     #define BOOST_CODECVT_DO_LENGTH_CONST