RFC 4880, "OpenPGP Message Format", November 2007Source of RFC: openpgp (sec)
Errata ID: 2231
Reported By: Constantin Hagemeier
Date Reported: 2010-04-28
Rejected by: Sean Turner
Date Rejected: 2010-07-20
Section 5.14. says:
A Modification Detection Code packet MUST have a length of 20 octets.
It should say:
A Modification Detection Code packet MUST have a body length of 20 octets.
The packet consists of header and body.
Similar to errata 2220 etc. It is indeed pedantic as submitter notes.