diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 29db5c7fce..ff522c5fb8 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 # Copyright 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");