diff --git a/grouping.go b/grouping.go
index 98399b9..6338a74 100644
--- a/grouping.go
+++ b/grouping.go
@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2021-2024 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
 package apg
 
 import "unicode"
diff --git a/grouping_test.go b/grouping_test.go
index 972cb52..e995b68 100644
--- a/grouping_test.go
+++ b/grouping_test.go
@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2021-2024 Winni Neessen <wn@neessen.dev>
+//
+// SPDX-License-Identifier: MIT
+
 package apg
 
 import "testing"