diff --git a/include/boost/endian/detail/intrinsic.hpp b/include/boost/endian/detail/intrinsic.hpp
index 8971085..6ead681 100644
--- a/include/boost/endian/detail/intrinsic.hpp
+++ b/include/boost/endian/detail/intrinsic.hpp
@@ -58,5 +58,7 @@
 # define BOOST_ENDIAN_INTRINSIC_MSG "no byte swap intrinsics"
 #endif
 
+#elif !defined(BOOST_ENDIAN_INTRINSIC_MSG)
+# define BOOST_ENDIAN_INTRINSIC_MSG "no byte swap intrinsics"
 #endif  // BOOST_ENDIAN_NO_INTRINSICS
 #endif  // BOOST_ENDIAN_INTRINSIC_HPP