diff --git a/synapse/federation/transport.py b/synapse/federation/transport.py
index b72d7b24d..8d8615208 100644
--- a/synapse/federation/transport.py
+++ b/synapse/federation/transport.py
@@ -143,7 +143,7 @@ class TransportLayer(object):
 
         args = {
             "v": event_tuples,
-            "limit": limit,
+            "limit": [str(limit)],
         }
 
         return self._do_request_for_transaction(