diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 773290692..d06033b98 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -105,6 +105,11 @@ class DataStore(RoomMemberStore, RoomStore,
             "processed": True,
         }
 
+        if hasattr(event, "outlier"):
+            vals["outlier"] = event.outlier
+        else:
+            vals["outlier"] = False
+
         if backfilled:
             if not self.min_token_deferred.called:
                 yield self.min_token_deferred
@@ -123,7 +128,7 @@ class DataStore(RoomMemberStore, RoomStore,
         except:
             logger.exception(
                 "Failed to persist, probably duplicate: %s",
-                event_id
+                event.event_id
             )
             return
 
diff --git a/synapse/storage/schema/im.sql b/synapse/storage/schema/im.sql
index ea04261ff..39a1ed703 100644
--- a/synapse/storage/schema/im.sql
+++ b/synapse/storage/schema/im.sql
@@ -22,6 +22,7 @@ CREATE TABLE IF NOT EXISTS events(
     content TEXT NOT NULL,
     unrecognized_keys TEXT,
     processed BOOL NOT NULL,
+    outlier BOOL NOT NULL,
     CONSTRAINT ev_uniq UNIQUE (event_id)
 );
 
diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index 8bc502483..87ae961cc 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -177,6 +177,7 @@ class StreamStore(SQLBaseStore):
             "((room_id IN (%(current)s)) OR "
             "(event_id IN (%(invites)s))) "
             "AND e.stream_ordering > ? AND e.stream_ordering < ? "
+            "AND e.outlier = 0 "
             "ORDER BY stream_ordering ASC LIMIT %(limit)d "
         ) % {
             "current": current_room_membership_sql,
@@ -224,7 +225,7 @@ class StreamStore(SQLBaseStore):
 
         sql = (
             "SELECT * FROM events "
-            "WHERE room_id = ? AND %(bounds)s "
+            "WHERE outlier = 0 AND room_id = ? AND %(bounds)s "
             "ORDER BY topological_ordering %(order)s, stream_ordering %(order)s %(limit)s "
         ) % {"bounds": bounds, "order": order, "limit": limit_str}