diff --git a/changelog.d/5967.bugfix b/changelog.d/5967.bugfix
new file mode 100644
index 0000000000000000000000000000000000000000..8d7bf5c2e907c7062539ab49a8309f6a1aa75d81
--- /dev/null
+++ b/changelog.d/5967.bugfix
@@ -0,0 +1 @@
+Fix list media admin API always returning an error.
diff --git a/synapse/rest/admin/media.py b/synapse/rest/admin/media.py
index f3f63f0be7116ef3087c6224968938486f3caadd..ed7086d09cb3a458933c8499fe9e063838f7637a 100644
--- a/synapse/rest/admin/media.py
+++ b/synapse/rest/admin/media.py
@@ -60,6 +60,7 @@ class ListMediaInRoom(RestServlet):
 
     def __init__(self, hs):
         self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
 
     @defer.inlineCallbacks
     def on_GET(self, request, room_id):