diff -up shadow-4.6/lib/getdef.c.login-prompt shadow-4.6/lib/getdef.c
--- shadow-4.6/lib/getdef.c.login-prompt	2018-04-29 18:42:37.000000000 +0200
+++ shadow-4.6/lib/getdef.c	2019-03-21 15:06:58.009280504 +0100
@@ -94,6 +94,7 @@ static struct itemdef def_table[] = {
 	{"KILLCHAR", NULL},
 	{"LOGIN_RETRIES", NULL},
 	{"LOGIN_TIMEOUT", NULL},
+	{"LOGIN_PLAIN_PROMPT", NULL},
 	{"LOG_OK_LOGINS", NULL},
 	{"LOG_UNKFAIL_ENAB", NULL},
 	{"MAIL_DIR", NULL},