--- a/plugins/mod_smacks.lua	Fri Nov 04 12:26:10 2022 +0000
+++ b/plugins/mod_smacks.lua	Sun Nov 13 18:16:59 2022 +0100
@@ -308,7 +308,8 @@
 	local resume_max;
 	local resume_token;
 	local resume = stanza.attr.resume;
-	if resume == "true" or resume == "1" then
+	if (resume == "true" or resume == "1") and session.username then
+		-- resumption on s2s is not currently supported
 		resume_token = new_id();
 		session_registry[jid.join(session.username, session.host, resume_token)] = session;
 		session.resumption_token = resume_token;