diff --git a/vona/federation/__init__.py b/vona/federation/__init__.py
index 050bc21..fedc2ae 100644
--- a/vona/federation/__init__.py
+++ b/vona/federation/__init__.py
@@ -209,7 +209,13 @@ async def receive_txn(txnId):
 	if "pdus" in parsed_data:
 		for pdu in parsed_data["pdus"]:
 			if "event_id" in pdu:
-				response["pdus"][pdu["event_id"]] = {}
+				# For v1 and v2 rooms
+				event_id = pdu["event_id"]
+			else:
+				# Assume room v4 or over as most rooms will be anyway
+				event_id = globals.make_ref_hash(pdu, 4)
+
+			response["pdus"][event_id] = {}
 
 	return jsonify(response)