--- a/plugins/muc/lock.lib.lua	Thu Oct 01 15:08:58 2020 +0100
+++ b/plugins/muc/lock.lib.lua	Wed Sep 30 09:50:33 2020 +0100
@@ -43,7 +43,7 @@
 module:hook("muc-occupant-pre-join", function(event)
 	if not event.is_new_room and is_locked(event.room) then -- Deny entry
 		module:log("debug", "Room is locked, denying entry");
-		event.origin.send(st.error_reply(event.stanza, "cancel", "item-not-found"));
+		event.origin.send(st.error_reply(event.stanza, "cancel", "item-not-found", nil, module.host));
 		return true;
 	end
 end, -30);