diff --git a/synapse/http/server.py b/synapse/http/server.py
index 165c684d0d..b19e578844 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -37,6 +37,7 @@ import collections
 import logging
 import urllib
 import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -416,7 +417,7 @@ def respond_with_json(request, code, json_object, send_cors=False,
             json_bytes = encode_canonical_json(json_object)
         else:
             # ujson doesn't like frozen_dicts.
-            json_bytes = ujson.dumps(json_object, ensure_ascii=False)
+            json_bytes = simplejson.dumps(json_object)
 
     return respond_with_json_bytes(
         request, code, json_bytes,
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index a0a8e4b8e4..eb91c0b293 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -33,7 +33,7 @@ from ._base import set_timeline_upper_limit
 import itertools
 import logging
 
-import ujson as json
+import simplejson as json
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index bbb6aa992c..25300c87be 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -37,7 +37,7 @@ from functools import wraps
 import synapse.metrics
 
 import logging
-import ujson as json
+import simplejson as json
 
 # these are only included to make the type annotations work
 from synapse.events import EventBase    # noqa: F401