diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 0cfd561139b4..3c8bc8808e56 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -752,6 +752,10 @@ async def on_make_join_request(
             # If our server is still only partially joined, we can't give a complete
             # response to /make_join, so return a 404 as we would if we weren't in the
             # room at all.
+            # The main reason we can't respond properly is that we need to know about
+            # the auth events for the join event that we would return.
+            # We also should not bother entertaining the /make_join since we cannot
+            # handle the /send_join.
             logger.info(
                 "Rejecting /make_join to %s because it's a partial state room", room_id
             )