diff --git a/synapse/rest/client/v2_alpha/room_keys.py b/synapse/rest/client/v2_alpha/room_keys.py
index afb8a36dd0..9f0172e6f5 100644
--- a/synapse/rest/client/v2_alpha/room_keys.py
+++ b/synapse/rest/client/v2_alpha/room_keys.py
@@ -19,7 +19,7 @@ from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
 from synapse.http.servlet import (
-    RestServlet, parse_json_object_from_request
+    RestServlet, parse_json_object_from_request, parse_string
 )
 from ._base import client_v2_patterns