diff --git a/CHANGES.rst b/CHANGES.rst
index dcf9adc95..3b3292823 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,12 @@
+Changes in synapse v0.26.1 (2018-03-15)
+=======================================
+
+Bug fixes:
+
+* Fix bug where an invalid event caused server to stop functioning correctly,
+  due to parsing and serializing bugs in ujson library.
+
+
 Changes in synapse v0.26.0 (2018-01-05)
 =======================================
 
diff --git a/synapse/__init__.py b/synapse/__init__.py
index ef8853bd2..80efad3a6 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.26.0"
+__version__ = "0.26.1"
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index 83206348e..db43219d2 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -17,7 +17,7 @@ from synapse.storage.presence import UserPresenceState
 from synapse.types import UserID, RoomID
 from twisted.internet import defer
 
-import ujson as json
+import simplejson as json
 import jsonschema
 from jsonschema import FormatChecker
 
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 668a90e49..ce2c87e40 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import ujson as json
+import simplejson as json
 import logging
 
 from canonicaljson import encode_canonical_json
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 21f1717dd..d7413833e 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -35,7 +35,7 @@ from canonicaljson import encode_canonical_json
 
 import logging
 import random
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -561,8 +561,8 @@ class MessageHandler(BaseHandler):
 
         # Ensure that we can round trip before trying to persist in db
         try:
-            dump = ujson.dumps(unfreeze(event.content))
-            ujson.loads(dump)
+            dump = simplejson.dumps(unfreeze(event.content))
+            simplejson.loads(dump)
         except Exception:
             logger.exception("Failed to encode content: %r", event.content)
             raise
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 25466cd29..f1e9002e4 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -36,7 +36,7 @@ from twisted.web.util import redirectTo
 import collections
 import logging
 import urllib
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -370,8 +370,7 @@ def respond_with_json(request, code, json_object, send_cors=False,
         if canonical_json or synapse.events.USE_FROZEN_DICTS:
             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/replication/tcp/commands.py b/synapse/replication/tcp/commands.py
index 171227cce..9633404f7 100644
--- a/synapse/replication/tcp/commands.py
+++ b/synapse/replication/tcp/commands.py
@@ -19,7 +19,7 @@ allowed to be sent by which side.
 """
 
 import logging
-import ujson as json
+import simplejson as json
 
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 75b735b47..80989731f 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -29,7 +29,7 @@ from synapse.http.servlet import (
 
 import logging
 import urllib
-import ujson as json
+import simplejson as json
 
 logger = logging.getLogger(__name__)
 
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/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 40d2e664e..a413cb622 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -35,7 +35,7 @@ import os
 import re
 import fnmatch
 import cgi
-import ujson as json
+import simplejson as json
 import urlparse
 import itertools
 import datetime
diff --git a/synapse/storage/account_data.py b/synapse/storage/account_data.py
index 56a0bde54..40a2ad8d0 100644
--- a/synapse/storage/account_data.py
+++ b/synapse/storage/account_data.py
@@ -18,7 +18,7 @@ from twisted.internet import defer
 
 from synapse.util.caches.descriptors import cached, cachedList, cachedInlineCallbacks
 
-import ujson as json
+import simplejson as json
 import logging
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 11a1b942f..8f3bff311 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -19,7 +19,7 @@ from . import engines
 
 from twisted.internet import defer
 
-import ujson as json
+import simplejson as json
 import logging
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/deviceinbox.py b/synapse/storage/deviceinbox.py
index 548e795da..a879e5bfc 100644
--- a/synapse/storage/deviceinbox.py
+++ b/synapse/storage/deviceinbox.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 import logging
-import ujson
+import simplejson
 
 from twisted.internet import defer
 
@@ -85,7 +85,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
             )
             rows = []
             for destination, edu in remote_messages_by_destination.items():
-                edu_json = ujson.dumps(edu)
+                edu_json = simplejson.dumps(edu)
                 rows.append((destination, stream_id, now_ms, edu_json))
             txn.executemany(sql, rows)
 
@@ -177,7 +177,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                     " WHERE user_id = ?"
                 )
                 txn.execute(sql, (user_id,))
-                message_json = ujson.dumps(messages_by_device["*"])
+                message_json = simplejson.dumps(messages_by_device["*"])
                 for row in txn:
                     # Add the message for all devices for this user on this
                     # server.
@@ -199,7 +199,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                     # Only insert into the local inbox if the device exists on
                     # this server
                     device = row[0]
-                    message_json = ujson.dumps(messages_by_device[device])
+                    message_json = simplejson.dumps(messages_by_device[device])
                     messages_json_for_user[device] = message_json
 
             if messages_json_for_user:
@@ -253,7 +253,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
             messages = []
             for row in txn:
                 stream_pos = row[0]
-                messages.append(ujson.loads(row[1]))
+                messages.append(simplejson.loads(row[1]))
             if len(messages) < limit:
                 stream_pos = current_stream_id
             return (messages, stream_pos)
@@ -389,7 +389,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
             messages = []
             for row in txn:
                 stream_pos = row[0]
-                messages.append(ujson.loads(row[1]))
+                messages.append(simplejson.loads(row[1]))
             if len(messages) < limit:
                 stream_pos = current_stream_id
             return (messages, stream_pos)
diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index bd2effdf3..712106b83 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-import ujson as json
+import simplejson as json
 
 from twisted.internet import defer
 
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index 2cebb203c..ff8538ddf 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -17,7 +17,7 @@ from twisted.internet import defer
 from synapse.util.caches.descriptors import cached
 
 from canonicaljson import encode_canonical_json
-import ujson as json
+import simplejson as json
 
 from ._base import SQLBaseStore
 
diff --git a/synapse/storage/event_push_actions.py b/synapse/storage/event_push_actions.py
index 8efe2fd4b..575d710d5 100644
--- a/synapse/storage/event_push_actions.py
+++ b/synapse/storage/event_push_actions.py
@@ -21,7 +21,7 @@ from synapse.types import RoomStreamToken
 from .stream import lower_bound
 
 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 d08f7571d..73658a992 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
@@ -56,7 +56,6 @@ event_counter = metrics.register_counter(
 
 def encode_json(json_object):
     if USE_FROZEN_DICTS:
-        # ujson doesn't like frozen_dicts
         return encode_canonical_json(json_object)
     else:
         return json.dumps(json_object, ensure_ascii=False)
diff --git a/synapse/storage/receipts.py b/synapse/storage/receipts.py
index 12b3cc7f5..2c3aa3369 100644
--- a/synapse/storage/receipts.py
+++ b/synapse/storage/receipts.py
@@ -20,7 +20,7 @@ from synapse.util.caches.stream_change_cache import StreamChangeCache
 from twisted.internet import defer
 
 import logging
-import ujson as json
+import simplejson as json
 
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index 23688430b..2051d8506 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -23,7 +23,7 @@ from .engines import PostgresEngine, Sqlite3Engine
 
 import collections
 import logging
-import ujson as json
+import simplejson as json
 import re
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 3e77fd390..c1ca29928 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -27,7 +27,7 @@ from synapse.api.constants import Membership, EventTypes
 from synapse.types import get_domain_from_id
 
 import logging
-import ujson as json
+import simplejson as json
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/schema/delta/25/fts.py b/synapse/storage/schema/delta/25/fts.py
index 4269ac69a..e7351c3ae 100644
--- a/synapse/storage/schema/delta/25/fts.py
+++ b/synapse/storage/schema/delta/25/fts.py
@@ -17,7 +17,7 @@ import logging
 from synapse.storage.prepare_database import get_statements
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -66,7 +66,7 @@ def run_create(cur, database_engine, *args, **kwargs):
             "max_stream_id_exclusive": max_stream_id + 1,
             "rows_inserted": 0,
         }
-        progress_json = ujson.dumps(progress)
+        progress_json = simplejson.dumps(progress)
 
         sql = (
             "INSERT into background_updates (update_name, progress_json)"
diff --git a/synapse/storage/schema/delta/27/ts.py b/synapse/storage/schema/delta/27/ts.py
index 71b12a273..c0176c41e 100644
--- a/synapse/storage/schema/delta/27/ts.py
+++ b/synapse/storage/schema/delta/27/ts.py
@@ -16,7 +16,7 @@ import logging
 
 from synapse.storage.prepare_database import get_statements
 
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
diff --git a/synapse/storage/schema/delta/31/search_update.py b/synapse/storage/schema/delta/31/search_update.py
index 470ae0c00..fe6b7d196 100644
--- a/synapse/storage/schema/delta/31/search_update.py
+++ b/synapse/storage/schema/delta/31/search_update.py
@@ -16,7 +16,7 @@ from synapse.storage.engines import PostgresEngine
 from synapse.storage.prepare_database import get_statements
 
 import logging
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -49,7 +49,7 @@ def run_create(cur, database_engine, *args, **kwargs):
             "rows_inserted": 0,
             "have_added_indexes": False,
         }
-        progress_json = ujson.dumps(progress)
+        progress_json = simplejson.dumps(progress)
 
         sql = (
             "INSERT into background_updates (update_name, progress_json)"
diff --git a/synapse/storage/schema/delta/33/event_fields.py b/synapse/storage/schema/delta/33/event_fields.py
index 83066cccc..1e002f9db 100644
--- a/synapse/storage/schema/delta/33/event_fields.py
+++ b/synapse/storage/schema/delta/33/event_fields.py
@@ -15,7 +15,7 @@
 from synapse.storage.prepare_database import get_statements
 
 import logging
-import ujson
+import simplejson
 
 logger = logging.getLogger(__name__)
 
@@ -44,7 +44,7 @@ def run_create(cur, database_engine, *args, **kwargs):
             "max_stream_id_exclusive": max_stream_id + 1,
             "rows_inserted": 0,
         }
-        progress_json = ujson.dumps(progress)
+        progress_json = simplejson.dumps(progress)
 
         sql = (
             "INSERT into background_updates (update_name, progress_json)"
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index 479b04c63..c19e4ea44 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -21,7 +21,7 @@ from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
 import logging
 import re
-import ujson as json
+import simplejson as json
 
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/tags.py b/synapse/storage/tags.py
index bff73f3f0..982a50052 100644
--- a/synapse/storage/tags.py
+++ b/synapse/storage/tags.py
@@ -17,7 +17,7 @@ from ._base import SQLBaseStore
 from synapse.util.caches.descriptors import cached
 from twisted.internet import defer
 
-import ujson as json
+import simplejson as json
 import logging
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/storage/transactions.py b/synapse/storage/transactions.py
index 8f61f7ffa..f825264ea 100644
--- a/synapse/storage/transactions.py
+++ b/synapse/storage/transactions.py
@@ -23,7 +23,7 @@ from canonicaljson import encode_canonical_json
 from collections import namedtuple
 
 import logging
-import ujson as json
+import simplejson as json
 
 logger = logging.getLogger(__name__)