[fetchmail]spambounce in 5.8.14

It appears that the recent clean up of bounce messages has borken
anti-spam bounce responses from Postfix, at least:

fetchmail: SMTP>. (EOM)
fetchmail: SMTP< 571 Error: content rejected
fetchmail: SMTP> RSET
fetchmail: SMTP< 250 Ok
           **** List = 0x810bbb0, val = 250 <--- SMTP Error checked
 not flushed
fetchmail: POP3> QUIT

The spam is not bounced, nor it is flushed from the mailbox.