diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 7eadcdd28..dde10967b 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -411,8 +411,13 @@ class FederationClient(FederationBase):
             return srvs
 
         batch_size = 20
-        for i in xrange(0, len(missing_events), batch_size):
-            batch = missing_events[i:i + batch_size]
+        while missing_events:
+            batch = []
+            try:
+                for _ in range(0, batch_size):
+                    batch.append(missing_events.pop())
+            except KeyError:
+                pass
 
             deferreds = [
                 self.get_pdu(
@@ -423,9 +428,9 @@ class FederationClient(FederationBase):
             ]
 
             res = yield defer.DeferredList(deferreds, consumeErrors=True)
-            for (result, val), (e_id, _) in res:
-                if result and val:
-                    signed_events.append(val)
+            for success, (result, e_id) in res:
+                if success and result:
+                    signed_events.append(result)
                 else:
                     failed_to_fetch.add(e_id)
 
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 40e9fda0e..35a01eecc 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -623,7 +623,7 @@ class FederationServer(FederationBase):
                     origin, pdu.room_id, pdu.event_id,
                 )
             except:
-                logger.warn("Failed to get state for event: %s", pdu.event_id)
+                logger.exception("Failed to get state for event: %s", pdu.event_id)
 
         yield self.handler.on_receive_pdu(
             origin,