diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
index c4f31f4c..8719cef7 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/decryption_verification/MessageMetadata.kt
@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package org.pgpainless.decryption_verification
 
 import org.bouncycastle.openpgp.PGPKeyRing