diff --git a/mautrix_telegram/abstract_user.py b/mautrix_telegram/abstract_user.py
index 512cedf6..7556b3cb 100644
--- a/mautrix_telegram/abstract_user.py
+++ b/mautrix_telegram/abstract_user.py
@@ -456,6 +456,7 @@ class AbstractUser(ABC):
             return
 
         if not portal or not portal.mxid:
+            # TODO This explodes on channels because the field is channel_id
             self.log.debug(f"Dropping own read receipt in unknown chat ({update.peer})")
             return