diff --git a/changelog.d/6555.bugfix b/changelog.d/6555.bugfix
new file mode 100644
index 0000000000..86a5a56cf6
--- /dev/null
+++ b/changelog.d/6555.bugfix
@@ -0,0 +1 @@
+Fix missing row in device_max_stream_id that could cause unable to decrypt errors after server restart.
\ No newline at end of file
diff --git a/synapse/storage/data_stores/main/deviceinbox.py b/synapse/storage/data_stores/main/deviceinbox.py
index 85cfa16850..0613b49f4a 100644
--- a/synapse/storage/data_stores/main/deviceinbox.py
+++ b/synapse/storage/data_stores/main/deviceinbox.py
@@ -358,21 +358,8 @@ class DeviceInboxStore(DeviceInboxWorkerStore, DeviceInboxBackgroundUpdateStore)
     def _add_messages_to_local_device_inbox_txn(
         self, txn, stream_id, messages_by_user_then_device
     ):
-        # Compatible method of performing an upsert
-        sql = "SELECT stream_id FROM device_max_stream_id"
-
-        txn.execute(sql)
-        rows = txn.fetchone()
-        if rows:
-            db_stream_id = rows[0]
-            if db_stream_id < stream_id:
-                # Insert the new stream_id
-                sql = "UPDATE device_max_stream_id SET stream_id = ?"
-        else:
-            # No rows, perform an insert
-            sql = "INSERT INTO device_max_stream_id (stream_id) VALUES (?)"
-
-        txn.execute(sql, (stream_id,))
+        sql = "UPDATE device_max_stream_id" " SET stream_id = ?" " WHERE stream_id < ?"
+        txn.execute(sql, (stream_id, stream_id))
 
         local_by_user_then_device = {}
         for user_id, messages_by_device in messages_by_user_then_device.items():
diff --git a/synapse/storage/data_stores/main/schema/delta/56/device_stream_id_insert.sql b/synapse/storage/data_stores/main/schema/delta/56/device_stream_id_insert.sql
new file mode 100644
index 0000000000..c2f557fde9
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/delta/56/device_stream_id_insert.sql
@@ -0,0 +1,20 @@
+/* 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.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- This line already existed in deltas/35/device_stream_id but was not included in the
+-- 54 full schema SQL. Add some SQL here to insert the missing row if it does not exist
+INSERT INTO device_max_stream_id (stream_id) SELECT 0 WHERE NOT EXISTS (
+    SELECT * from device_max_stream_id
+);
\ No newline at end of file
diff --git a/synapse/storage/data_stores/main/schema/full_schemas/54/stream_positions.sql b/synapse/storage/data_stores/main/schema/full_schemas/54/stream_positions.sql
index c265fd20e2..91d21b2921 100644
--- a/synapse/storage/data_stores/main/schema/full_schemas/54/stream_positions.sql
+++ b/synapse/storage/data_stores/main/schema/full_schemas/54/stream_positions.sql
@@ -5,3 +5,4 @@ INSERT INTO federation_stream_position (type, stream_id) SELECT 'events', coales
 INSERT INTO user_directory_stream_pos (stream_id) VALUES (0);
 INSERT INTO stats_stream_pos (stream_id) VALUES (0);
 INSERT INTO event_push_summary_stream_ordering (stream_ordering) VALUES (0);
+-- device_max_stream_id is handled separately in 56/device_stream_id_insert.sql
\ No newline at end of file