Debian: spamc skipped message, greater than max message

Log entry:

Apr 23 13:14:40 ahso2 spamc[18922]: skipped message, greater than max message size (512000 bytes)

spamc is called in /etc/postfix/master/cf:

spamassassin
          unix  -       n       n       -       -       pipe
  flags=Rq user=nobody argv=/usr/bin/spamc --max-size 2097152 -u ${user} -e /usr/sbin/sendmail -oi -f ${sender} ${recipient}