--- a/mod_log_auth/mod_log_auth.lua	Wed Apr 19 06:38:08 2017 +0200
+++ b/mod_log_auth/mod_log_auth.lua	Wed Apr 19 06:45:49 2017 +0200
@@ -5,8 +5,9 @@
 if mode == "failure" or mode == "all" then
 	module:hook("authentication-failure", function (event)
 		local session = event.session;
+		local username = session.username or session.sasl_handler and session.sasl_handler.username or "?";
 		module:log("info", "Failed authentication attempt (%s) for user %s from IP: %s",
-			event.condition or "unknown-condition", session.username or session.sasl_handler.username or "?", session.ip or "?");
+			event.condition or "unknown-condition", username, session.ip or "?");
 	end);
 end