how to prevent amavis from removing Authentication Results?

[Marko Weber]

when i send from one of my servers a mail to my new mailserver
with amavis 2.7.1 i see this in the logs

May 22 16:12:29 mail amavis[3617]: (03617-01) deleted: 
Authentication-Results: mail.xxxxxmail.de; x-dkim-rep=neutral (0) 
header.d=xxxxxertig.de

May 22 16:12:29 mail amavis[3617]: (03617-01) deleted: 
Authentication-Results: mail.xxxxxmail.de; dkim=pass (1024-bit 
key)\n\theader.i=xxxxfertig.de header.b=TbAL96p2; dkim-adsp=pass


how can i tell amavis TO NOT DELETE this entries?

i laready set:

$enable_dkim_verification = 0;  # enable DKIM signatures verification
$enable_dkim_signing = 0;    # load DKIM signing code, keys defined by 
dkim_key


any ideas?