diff --git a/metropolis/test/nanoswitch/socks.go b/metropolis/test/nanoswitch/socks.go
index 1230903..4ba1d0a 100644
--- a/metropolis/test/nanoswitch/socks.go
+++ b/metropolis/test/nanoswitch/socks.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package main
 
 import (