https://svn.apache.org/viewvc/spamassassin/trunk/lib/Mail/SpamAssassin/DnsResolver.pm?r1=1909910&r2=1909909&pathrev=1909910
--- a/lib/Mail/SpamAssassin/DnsResolver.pm
+++ b/lib/Mail/SpamAssassin/DnsResolver.pm
@@ -599,7 +599,11 @@
     my $udp_payload_size = $self->{conf}->{dns_options}->{edns};
     if ($udp_payload_size && $udp_payload_size > 512) {
       # dbg("dns: adding EDNS ext, UDP payload size %d", $udp_payload_size);
-      $packet->edns->size($udp_payload_size);
+      if ($packet->edns->can('udpsize')) { # since Net::DNS 1.38
+        $packet->edns->udpsize($udp_payload_size);
+      } else {
+        $packet->edns->size($udp_payload_size);
+      }
     }
   }