--- foo/foo/foo/boost/predef/other/endian.h
+++ foo/foo/foo/boost/predef/other/endian.h
@@ -77,7 +77,7 @@
 #           undef BOOST_ENDIAN_LITTLE_BYTE
 #           define BOOST_ENDIAN_LITTLE_BYTE BOOST_VERSION_NUMBER_AVAILABLE
 #       endif
-#       if (__BYTE_ORDER == __PDP_ENDIAN)
+#       if defined(__PDP_ENDIAN) && (__BYTE_ORDER == __PDP_ENDIAN)
 #           undef BOOST_ENDIAN_LITTLE_WORD
 #           define BOOST_ENDIAN_LITTLE_WORD BOOST_VERSION_NUMBER_AVAILABLE
 #       endif