diff --git a/lib/setup.h b/lib/setup.h
index d687823665..c3a308abd1 100644
--- a/lib/setup.h
+++ b/lib/setup.h
@@ -272,6 +272,9 @@
 #ifdef word
 #undef word
 #endif
+#ifdef byte
+#undef byte
+#endif
 
 #else /* MSDOS */