diff --git a/services/federation_publish.py b/services/federation_publish.py
index d20053d..90843f3 100644
--- a/services/federation_publish.py
+++ b/services/federation_publish.py
@@ -53,6 +53,10 @@ async def try_publish(
     elif activity_type == "Delete":
         return  # never published, nothing to delete
 
+    # Delete must reference the same object id Mastodon received in Create
+    if activity_type == "Delete" and existing:
+        object_data["id"] = existing.activity_id + "/object"
+
     try:
         await services.federation.publish_activity(
             session,