diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 48548f8c4082..9989b7659179 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -154,7 +154,8 @@ def serialize_event(e, time_now_ms, as_client_event=True,
 
     if "redacted_because" in e.unsigned:
         d["unsigned"]["redacted_because"] = serialize_event(
-            e.unsigned["redacted_because"], time_now_ms
+            e.unsigned["redacted_because"], time_now_ms,
+            event_format=event_format
         )
 
     if token_id is not None:
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 8601f2217936..4c5a2353b2be 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -387,7 +387,7 @@ def incremental_sync_with_gap(self, sync_config, since_token):
                 else:
                     prev_batch = now_token
 
-                state = yield self.check_joined_room(
+                state, limited = yield self.check_joined_room(
                     sync_config, room_id, state
                 )
 
@@ -396,7 +396,7 @@ def incremental_sync_with_gap(self, sync_config, since_token):
                     timeline=TimelineBatch(
                         events=recents,
                         prev_batch=prev_batch,
-                        limited=False,
+                        limited=limited,
                     ),
                     state=state,
                     ephemeral=typing_by_room.get(room_id, [])
@@ -520,7 +520,7 @@ def incremental_sync_with_gap_for_room(self, room_id, sync_config,
             current_state=current_state_events,
         )
 
-        state_events_delta = yield self.check_joined_room(
+        state_events_delta, _ = yield self.check_joined_room(
             sync_config, room_id, state_events_delta
         )
 
@@ -627,6 +627,7 @@ def compute_state_delta(self, since_token, previous_state, current_state):
     @defer.inlineCallbacks
     def check_joined_room(self, sync_config, room_id, state_delta):
         joined = False
+        limited = False
         for event in state_delta:
             if (
                 event.type == EventTypes.Member
@@ -638,5 +639,6 @@ def check_joined_room(self, sync_config, room_id, state_delta):
         if joined:
             res = yield self.state_handler.get_current_state(room_id)
             state_delta = res.values()
+            limited = True
 
-        defer.returnValue(state_delta)
+        defer.returnValue((state_delta, limited))
diff --git a/tox.ini b/tox.ini
index a69948484f63..01b23e6bd967 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,6 +19,7 @@ commands =
     check-manifest
 
 [testenv:pep8]
+skip_install = True
 basepython = python2.7
 deps =
     flake8