diff --git a/osbase/msguid/msguid.go b/osbase/msguid/msguid.go
index 4074f8a..b5f4b6a 100644
--- a/osbase/msguid/msguid.go
+++ b/osbase/msguid/msguid.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // Package msguid provides functions to convert UUIDs/GUIDs to and from
 // Microsoft's idiosyncratic "mixed-endian" format.
 // See https://uefi.org/specs/UEFI/2.10/Apx_A_GUID_and_Time_Formats.html#text-representation-relationships-apxa-guid-and-time-formats
diff --git a/osbase/msguid/msguid_test.go b/osbase/msguid/msguid_test.go
index b8cdfea..226c7a6 100644
--- a/osbase/msguid/msguid_test.go
+++ b/osbase/msguid/msguid_test.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package msguid
 
 import (