diff --git a/synapse/http/server.py b/synapse/http/server.py
index 4b567215c812b085d9d5da9943d16d317ae7c899..3c7a0ef97aa35154edd1f6eb050a86b0910138e6 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -38,6 +38,7 @@ import collections
 import logging
 import urllib
 import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -462,7 +463,7 @@ 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 a0a8e4b8e46c6af7498c2883ddebc6f4c41e72d1..eb91c0b2934cceae937a0085e9016e469ddbbfbb 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 38908781700b09be0ab516d276c491e2de9d393d..9fc65229fd80626ec57261b5756c88e961d60d2e 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -38,7 +38,7 @@ 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
diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index 86c3b48ad40a0003045388e070755e43a6f93810..2e23dd78ba983d4a853e8c0250c9d2cb279253a8 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -28,7 +28,7 @@ from synapse.api.errors import SynapseError
 from collections import namedtuple
 
 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