1 files changed, 2 insertions, 3 deletions

diff --git a/src/mailman/model/messagestore.py b/src/mailman/model/messagestore.py
index 0b8a0ac78..19fa8133f 100644
--- a/src/mailman/model/messagestore.py
+++ b/src/mailman/model/messagestore.py
@@ -117,9 +117,8 @@ class MessageStore:
     def get_message_by_hash(self, store, message_id_hash):
         # It's possible the hash came from a message header, in which case it
         # will be a Unicode.  However when coming from source code, it may be
-        # an 8-string.  Coerce to the latter if necessary; it must be
-        # US-ASCII.
-        if isinstance(message_id_hash, unicode):
+        # bytes object.  Coerce to the latter if necessary; it must be ASCII.
+        if not isinstance(message_id_hash, bytes):
             message_id_hash = message_id_hash.encode('ascii')
         row = store.query(Message).filter_by(
             message_id_hash=message_id_hash).first()