Problems with content-length on MDN HTTP response

Hello,
We are facing the following issue when using mendelson as an AS2 http client sending an EDI order and requesting synchronous signed MDN response:
MessageHTTPUploader.performUpload: [ConnectionClosedException]: Premature end of Content-Length delimited message body (expected: 2249; received: 2248)

I've tried to activate the HTTP request log (debug) however the log file remains empty.

Anybody a clue on this HTTP response error?

Thanks.