diff --git a/cobs.c b/cobs.c
index 55d0588..a8e0554 100644
--- a/cobs.c
+++ b/cobs.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: Unlicense OR 0BSD
 #include "cobs.h"
 
 #define COBS_ISV COBS_INPLACE_SENTINEL_VALUE
diff --git a/cobs.h b/cobs.h
index af679fa..4d7192a 100644
--- a/cobs.h
+++ b/cobs.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: Unlicense OR 0BSD
 #pragma once
 
 #include <stdbool.h>