1 files changed, 6 insertions, 3 deletions

diff --git a/src/mailman/model/messagestore.py b/src/mailman/model/messagestore.py
index 225d3d1ce..19fa8133f 100644
--- a/src/mailman/model/messagestore.py
+++ b/src/mailman/model/messagestore.py
@@ -66,7 +66,7 @@ class MessageStore:
                 'Message ID already exists in message store: {0}'.format(
                     message_id))
         shaobj = hashlib.sha1(message_id)
-        hash32 = base64.b32encode(shaobj.digest()).decode('ascii')
+        hash32 = base64.b32encode(shaobj.digest())
         del message['X-Message-ID-Hash']
         message['X-Message-ID-Hash'] = hash32
         # Calculate the path on disk where we're going to store this message
@@ -115,8 +115,11 @@ class MessageStore:
 
     @dbconnection
     def get_message_by_hash(self, store, message_id_hash):
-        if isinstance(message_id_hash, bytes):
-            message_id_hash = message_id_hash.decode('utf-8')
+        # 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
+        # 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()
         if row is None: