diff --git a/synapse/http/server.py b/synapse/http/server.py
index 4b567215c..3c7a0ef97 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 a0a8e4b8e..eb91c0b29 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 389087817..9fc65229f 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 86c3b48ad..2e23dd78b 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