1 files changed, 3 insertions, 1 deletions
diff --git a/synapse/events/builder.py b/synapse/events/builder.py
index c82745275f..a254548c6c 100644
--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -173,7 +173,9 @@ class EventBuilder:
         if self.is_state():
             event_dict["state_key"] = self._state_key
 
-        if self._redacts is not None:
+        # MSC2174 moves the redacts property to the content, it is invalid to
+        # provide it as a top-level property.
+        if self._redacts is not None and not self.room_version.msc2176_redaction_rules:
             event_dict["redacts"] = self._redacts
 
         if self._origin_server_ts is not None: