1 files changed, 8 insertions, 3 deletions
diff --git a/synapse/replication/tcp/streams/_base.py b/synapse/replication/tcp/streams/_base.py
index 54dccd15a6..61b282ab2d 100644
--- a/synapse/replication/tcp/streams/_base.py
+++ b/synapse/replication/tcp/streams/_base.py
@@ -240,13 +240,18 @@ class BackfillStream(Stream):
     ROW_TYPE = BackfillStreamRow
 
     def __init__(self, hs):
-        store = hs.get_datastore()
+        self.store = hs.get_datastore()
         super().__init__(
             hs.get_instance_name(),
-            current_token_without_instance(store.get_current_backfill_token),
-            store.get_all_new_backfill_event_rows,
+            self._current_token,
+            self.store.get_all_new_backfill_event_rows,
         )
 
+    def _current_token(self, instance_name: str) -> int:
+        # The backfill stream over replication operates on *positive* numbers,
+        # which means we need to negate it.
+        return -self.store._backfill_id_gen.get_current_token_for_writer(instance_name)
+
 
 class PresenceStream(Stream):
     PresenceStreamRow = namedtuple(