diff --git a/usr.sbin/ppp/mp.h b/usr.sbin/ppp/mp.h
index 607ba74881c..e33a7edd104 100644
--- a/usr.sbin/ppp/mp.h
+++ b/usr.sbin/ppp/mp.h
@@ -56,7 +56,7 @@ struct enddisc {
 
 struct peerid {
   struct enddisc enddisc;	/* Peers endpoint discriminator */
-  char authname[50];		/* Peers name (authenticated) */
+  char authname[AUTHLEN];	/* Peers name (authenticated) */
 };
 
 struct mpserver {