2 files changed, 9 insertions, 2 deletions
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index dc49df0812..7a51d0a22f 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -97,13 +97,16 @@ class DefaultDictProperty(DictProperty):
 
 
 class _EventInternalMetadata:
-    __slots__ = ["_dict"]
+    __slots__ = ["_dict", "stream_ordering"]
 
     def __init__(self, internal_metadata_dict: JsonDict):
         # we have to copy the dict, because it turns out that the same dict is
         # reused. TODO: fix that
         self._dict = dict(internal_metadata_dict)
 
+        # the stream ordering of this event. None, until it has been persisted.
+        self.stream_ordering = None  # type: Optional[int]
+
     outlier = DictProperty("outlier")  # type: bool
     out_of_band_membership = DictProperty("out_of_band_membership")  # type: bool
     send_on_behalf_of = DictProperty("send_on_behalf_of")  # type: str
@@ -113,7 +116,6 @@ class _EventInternalMetadata:
     redacted = DictProperty("redacted")  # type: bool
     txn_id = DictProperty("txn_id")  # type: str
     token_id = DictProperty("token_id")  # type: str
-    stream_ordering = DictProperty("stream_ordering")  # type: int
 
     # XXX: These are set by StreamWorkerStore._set_before_and_after.
     # I'm pretty sure that these are never persisted to the database, so shouldn't
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 32c73d3413..355cbe05f1 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -49,6 +49,11 @@ def prune_event(event: EventBase) -> EventBase:
         pruned_event_dict, event.room_version, event.internal_metadata.get_dict()
     )
 
+    # copy the internal fields
+    pruned_event.internal_metadata.stream_ordering = (
+        event.internal_metadata.stream_ordering
+    )
+
     # Mark the event as redacted
     pruned_event.internal_metadata.redacted = True