diff --git a/pkg/mapper_cache/lru/lru.go b/pkg/mapper_cache/lru/lru.go
index dc8d9ac..e6739ee 100644
--- a/pkg/mapper_cache/lru/lru.go
+++ b/pkg/mapper_cache/lru/lru.go
@@ -1,3 +1,16 @@
+// Copyright 2021 The Prometheus Authors
+// 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
+//
+// http://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 lru
 
 import (
diff --git a/pkg/mapper_cache/metrics.go b/pkg/mapper_cache/metrics.go
index a6fa3f6..f3d76f7 100644
--- a/pkg/mapper_cache/metrics.go
+++ b/pkg/mapper_cache/metrics.go
@@ -1,3 +1,16 @@
+// Copyright 2021 The Prometheus Authors
+// 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
+//
+// http://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 mapper_cache
 
 import "github.com/prometheus/client_golang/prometheus"
diff --git a/pkg/mapper_cache/randomreplacement/randomreplacement.go b/pkg/mapper_cache/randomreplacement/randomreplacement.go
index 0bc470f..1dfaa28 100644
--- a/pkg/mapper_cache/randomreplacement/randomreplacement.go
+++ b/pkg/mapper_cache/randomreplacement/randomreplacement.go
@@ -1,3 +1,16 @@
+// Copyright 2021 The Prometheus Authors
+// 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
+//
+// http://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 randomreplacement
 
 import (