diff --git a/build/toolbase/label.go b/build/toolbase/label.go
index 5d033b3..a16860d 100644
--- a/build/toolbase/label.go
+++ b/build/toolbase/label.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package toolbase
 
 import (