diff --git a/mautrix_telegram/portal/metadata.py b/mautrix_telegram/portal/metadata.py
index 97d9dd05..578b0b52 100644
--- a/mautrix_telegram/portal/metadata.py
+++ b/mautrix_telegram/portal/metadata.py
@@ -249,6 +249,9 @@ class PortalMetadata(BasePortal, ABC):
                                   ) -> Optional[RoomID]:
         direct = self.peer_type == "user"
 
+        if invites is None:
+            invites = []
+
         if self.mxid:
             return self.mxid