varnish unsetting X-Forwarded-For

I am running varnish-4.0.4-3 on centos7. In the varnish logs, I find: 23 ReqUnset c X-Forwarded-For: 172.16.1.2 23 ReqHeader c X-Forwarded-For: 172.16.1.2, 127.0.0.1 How can I disable X-Forwarded-For modification please?