diff --git a/metropolis/cli/metroctl/main.go b/metropolis/cli/metroctl/main.go
index 6d26d4c..b5731c6 100644
--- a/metropolis/cli/metroctl/main.go
+++ b/metropolis/cli/metroctl/main.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package main
 
 import (