1 files changed, 6 insertions, 4 deletions
diff --git a/synapse/rest/client/receipts.py b/synapse/rest/client/receipts.py
index 409bfd43c1..c6108fc5eb 100644
--- a/synapse/rest/client/receipts.py
+++ b/synapse/rest/client/receipts.py
@@ -44,11 +44,13 @@ class ReceiptRestServlet(RestServlet):
         self.read_marker_handler = hs.get_read_marker_handler()
         self.presence_handler = hs.get_presence_handler()
 
-        self._known_receipt_types = {ReceiptTypes.READ}
+        self._known_receipt_types = {
+            ReceiptTypes.READ,
+            ReceiptTypes.READ_PRIVATE,
+            ReceiptTypes.FULLY_READ,
+        }
         if hs.config.experimental.msc2285_enabled:
-            self._known_receipt_types.update(
-                (ReceiptTypes.READ_PRIVATE, ReceiptTypes.FULLY_READ)
-            )
+            self._known_receipt_types.add(ReceiptTypes.UNSTABLE_READ_PRIVATE)
 
     async def on_POST(
         self, request: SynapseRequest, room_id: str, receipt_type: str, event_id: str