diff --git a/build/mirror_proxy/main.go b/build/mirror_proxy/main.go
index 9dd0d0e..101a735 100644
--- a/build/mirror_proxy/main.go
+++ b/build/mirror_proxy/main.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package main
 
 import (