diff --git a/include/langinfo.h b/include/langinfo.h
index 2f12f11915c..4e62311e58f 100644
--- a/include/langinfo.h
+++ b/include/langinfo.h
@@ -102,6 +102,8 @@
 
 #define	CRNCYSTR	56	/* currency symbol */
 
+#define	D_MD_ORDER	57	/* month/day order (local extension) */
+
 __BEGIN_DECLS
 char *nl_langinfo(nl_item);
 __END_DECLS