diff --git a/syncmap.go b/syncmap.go
index 02d8e07..d4678c8 100644
--- a/syncmap.go
+++ b/syncmap.go
@@ -1,4 +1,5 @@
-// Copyright 2026 AxonOps Limited.
+// Copyright 2023 Richard Gooding
+// Modifications Copyright 2026 AxonOps Limited
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -11,6 +12,9 @@
 // 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.
+//
+// This file is a fork of github.com/rgooding/go-syncmap; see NOTICE
+// for the upstream attribution.
 
 package syncmap