diff --git a/usr.sbin/pwd_mkdb/pwd_mkdb.c b/usr.sbin/pwd_mkdb/pwd_mkdb.c
index 7f6affb1f840..f62b898259d0 100644
--- a/usr.sbin/pwd_mkdb/pwd_mkdb.c
+++ b/usr.sbin/pwd_mkdb/pwd_mkdb.c
@@ -166,6 +166,8 @@ main(int argc, char *argv[])
 
 	if (argc != 1 || (username && (*username == '+' || *username == '-')))
 		usage();
+	if (lflag)
+		warnx("legacy (v3) database format support is deprecated");
 
 	/*
 	 * This could be changed to allow the user to interrupt.