diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index f0430b2cb..299493af9 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -18,8 +18,6 @@ from twisted.internet import defer
 
 from synapse.events.utils import prune_event
 
-from syutil.jsonutil import encode_canonical_json
-
 from synapse.crypto.event_signing import check_event_content_hash
 
 from synapse.api.errors import SynapseError
@@ -120,16 +118,15 @@ class FederationBase(object):
             )
         except SynapseError:
             logger.warn(
-                "Signature check failed for %s redacted to %s",
-                encode_canonical_json(pdu.get_pdu_json()),
-                encode_canonical_json(redacted_pdu_json),
+                "Signature check failed for %s",
+                pdu.event_id,
             )
             raise
 
         if not check_event_content_hash(pdu):
             logger.warn(
-                "Event content has been tampered, redacting %s, %s",
-                pdu.event_id, encode_canonical_json(pdu.get_dict())
+                "Event content has been tampered, redacting.",
+                pdu.event_id,
             )
             defer.returnValue(redacted_event)
 
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 5503d9ae8..b5d882fd6 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -247,9 +247,15 @@ class FederationHandler(BaseHandler):
             if set(e_id for e_id, _ in ev.prev_events) - event_ids
         ]
 
+        logger.info(
+            "backfill: Got %d events with %d edges",
+            len(events), len(edges),
+        )
+
         # For each edge get the current state.
 
         auth_events = {}
+        state_events = {}
         events_to_state = {}
         for e_id in edges:
             state, auth = yield self.replication_layer.get_state_for_room(
@@ -258,12 +264,46 @@ class FederationHandler(BaseHandler):
                 event_id=e_id
             )
             auth_events.update({a.event_id: a for a in auth})
+            auth_events.update({s.event_id: s for s in state})
+            state_events.update({s.event_id: s for s in state})
             events_to_state[e_id] = state
 
+        seen_events = yield self.store.have_events(
+            set(auth_events.keys()) | set(state_events.keys())
+        )
+
+        all_events = events + state_events.values() + auth_events.values()
+        required_auth = set(
+            a_id for event in all_events for a_id, _ in event.auth_events
+        )
+
+        missing_auth = required_auth - set(auth_events)
+        results = yield defer.gatherResults(
+            [
+                self.replication_layer.get_pdu(
+                    [dest],
+                    event_id,
+                    outlier=True,
+                    timeout=10000,
+                )
+                for event_id in missing_auth
+            ],
+            consumeErrors=True
+        ).addErrback(unwrapFirstError)
+        auth_events.update({a.event_id: a for a in results})
+
         yield defer.gatherResults(
             [
-                self._handle_new_event(dest, a)
+                self._handle_new_event(
+                    dest, a,
+                    auth_events={
+                        (auth_events[a_id].type, auth_events[a_id].state_key):
+                        auth_events[a_id]
+                        for a_id, _ in a.auth_events
+                    },
+                )
                 for a in auth_events.values()
+                if a.event_id not in seen_events
             ],
             consumeErrors=True,
         ).addErrback(unwrapFirstError)
@@ -274,6 +314,11 @@ class FederationHandler(BaseHandler):
                     dest, event_map[e_id],
                     state=events_to_state[e_id],
                     backfilled=True,
+                    auth_events={
+                        (auth_events[a_id].type, auth_events[a_id].state_key):
+                        auth_events[a_id]
+                        for a_id, _ in event_map[e_id].auth_events
+                    },
                 )
                 for e_id in events_to_state
             ],