diff --git a/include/linux/timer.h b/include/linux/timer.h
index 6383c52..ac66f29 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _LINUX_TIMER_H
 #define _LINUX_TIMER_H