[syslog-ng]Changing what source port syslog-ng uses, when sending a syslog

Hi Is there a way to change what source port syslog-ng uses, when it is sending a syslog ? I can see in our firewall log that it uses a high port Deny udp src inside:xxxx/32772 dst outside:xxx/514 by access-group "FromInside4" - Henning