diff --git a/lib/port.c b/lib/port.c
index 05b95651..60ff8989 100644
--- a/lib/port.c
+++ b/lib/port.c
@@ -168,7 +168,7 @@ again:
 	}
 	*cp = '\0';
 	cp++;
-	port.pt_names[j + 1] = NULL;
+	port.pt_names[j] = NULL;
 
 	/*
 	 * Get the list of user names.  It is the second colon