1 files changed, 5 insertions, 2 deletions
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index b3bab1aa52..a3b0c0a3e4 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
-# Copyright 2018 New Vector Ltd
+# Copyright 2017-2018 New Vector Ltd
+# Copyright 2019 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -238,14 +239,16 @@ class InteractiveAuthIncompleteError(Exception):
     (This indicates we should return a 401 with 'result' as the body)
 
     Attributes:
+        session_id: The ID of the ongoing interactive auth session.
         result: the server response to the request, which should be
             passed back to the client
     """
 
-    def __init__(self, result: "JsonDict"):
+    def __init__(self, session_id: str, result: "JsonDict"):
         super(InteractiveAuthIncompleteError, self).__init__(
             "Interactive auth not yet complete"
         )
+        self.session_id = session_id
         self.result = result