diff --git a/service/udp_linux.go b/service/udp_linux.go
index 9292b970..788f18f9 100644
--- a/service/udp_linux.go
+++ b/service/udp_linux.go
@@ -28,13 +28,13 @@ import (
 )
 
 type udpListener struct {
+	// The validator to be used to validate target IP addresses.
+	targetIPValidator onet.TargetIPValidator
+
 	// NAT mapping timeout is the default time a mapping will stay active
 	// without packets traversing the NAT, applied to non-DNS packets.
 	timeout time.Duration
 
-	// The validator to be used to validate target IP addresses.
-	targetIPValidator onet.TargetIPValidator
-
 	// fwmark can be used in conjunction with other Linux networking features like cgroups, network
 	// namespaces, and TC (Traffic Control) for sophisticated network management.
 	// Value of 0 disables fwmark (SO_MARK) (Linux only)