--- a/mod_muc_moderation/mod_muc_moderation.lua	Sat Dec 04 16:17:55 2021 +0100
+++ b/mod_muc_moderation/mod_muc_moderation.lua	Sat Dec 04 23:11:16 2021 +0100
@@ -66,7 +66,7 @@
 	if not actor_nick then
 		local reserved_nickname = room:get_affiliation_data(jid.bare(actor), "reserved_nickname");
 		if reserved_nickname then
-			actor_nick = jid.join(room.jid, reserved_nickname);
+			actor_nick = room.jid .. "/" .. reserved_nickname;
 		end
 	end