diff --git a/internal/errors/ngt_test.go b/internal/errors/ngt_test.go
index f89e5d90a5..ad55bdcb38 100644
--- a/internal/errors/ngt_test.go
+++ b/internal/errors/ngt_test.go
@@ -1,3 +1,18 @@
+//
+// Copyright (C) 2019-2021 vdaas.org vald team <vald@vdaas.org>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
 package errors
 
 import (