diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index a8cd8d9943..b06ea440af 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -958,7 +958,7 @@ class EventCreationHandler:
         # Pass on the outlier property from the builder to the event
         # after it is created
         if builder.internal_metadata.outlier:
-            event.internal_metadata.outlier = builder.internal_metadata.outlier
+            event.internal_metadata.outlier = True
             context = EventContext.for_outlier()
 
         if requester: