diff --git a/pkg/strutil/merge_test.go b/pkg/strutil/merge_test.go
index 2c127d2217e..8472ca1f869 100644
--- a/pkg/strutil/merge_test.go
+++ b/pkg/strutil/merge_test.go
@@ -1,3 +1,6 @@
+// Copyright (c) The Thanos Authors.
+// Licensed under the Apache License 2.0.
+
 package strutil
 
 import (