diff --git a/include/boost/detail/endian.hpp b/include/boost/detail/endian.hpp
index 6936dba..6394d92 100644
--- a/include/boost/detail/endian.hpp
+++ b/include/boost/detail/endian.hpp
@@ -42,10 +42,10 @@
 #  error Unknown machine endianness detected.
 # endif
 # define BOOST_BYTE_ORDER __BYTE_ORDER
-#elif defined(_BIG_ENDIAN)
+#elif defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
 # define BOOST_BIG_ENDIAN
 # define BOOST_BYTE_ORDER 4321
-#elif defined(_LITTLE_ENDIAN)
+#elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)
 # define BOOST_LITTLE_ENDIAN
 # define BOOST_BYTE_ORDER 1234
 #elif defined(__sparc) || defined(__sparc__) \