--- a/plugins/mod_saslauth.lua	Mon Nov 23 20:39:47 2020 +0000
+++ b/plugins/mod_saslauth.lua	Mon Nov 23 21:56:26 2020 +0100
@@ -260,7 +260,10 @@
 			-- FIXME: would be nice to have this check only once and not for every socket
 			if sasl_handler.add_cb_handler then
 				local socket = origin.conn:socket();
-				if socket.getpeerfinished then
+				local info = socket.info and socket:info();
+				if info.protocol == "TLSv1.3" then
+					log("debug", "Channel binding 'tls-unique' undefined in context of TLS 1.3");
+				elseif socket.getpeerfinished and socket:getpeerfinished() then
 					log("debug", "Channel binding 'tls-unique' supported");
 					sasl_handler:add_cb_handler("tls-unique", tls_unique);
 				else