diff --git a/addons/fetchmail/models/fetchmail.py b/addons/fetchmail/models/fetchmail.py
index d12b9ec72a0..e03ef88ac44 100644
--- a/addons/fetchmail/models/fetchmail.py
+++ b/addons/fetchmail/models/fetchmail.py
@@ -204,7 +204,7 @@ class FetchmailServer(models.Model):
                         pop_server.list()
                         for num in range(1, min(MAX_POP_MESSAGES, num_messages) + 1):
                             (header, messages, octets) = pop_server.retr(num)
-                            message = '\n'.join(messages)
+                            message = (b'\n').join(messages)
                             res_id = None
                             try:
                                 res_id = MailThread.with_context(**additionnal_context).message_process(server.object_id.model, message, save_original=server.original, strip_attachments=(not server.attach))