diff --git a/dns_challenge.go b/dns_challenge.go
index 2eab8aef48d41453122948f9b2b70cd4cea3ced8..60755b451ec47199b62f230633dbc951843cbd04 100644
--- a/dns_challenge.go
+++ b/dns_challenge.go
@@ -110,6 +110,7 @@ func (d *dnsValidator) Fulfill(ctx context.Context, client *acme.Client, domain
 }
 
 func (d *dnsValidator) updateNS(ctx context.Context, ns, zone, fqdn, value string, remove bool) error {
+	log.Printf("updateNS(%s, %s, %s, %s, %v)", ns, zone, fqdn, value, remove)
 	rrs := d.makeRR(fqdn, value, rfc2136Timeout)
 	m := d.makeMsg(zone, rrs, remove)
 	c := d.client()