diff --git a/osbase/net/dns/testhelpers.go b/osbase/net/dns/testhelpers.go
index b8943fd..56d3b70 100644
--- a/osbase/net/dns/testhelpers.go
+++ b/osbase/net/dns/testhelpers.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package dns
 
 import (