diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 0bc0a35..46e4c749 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  *  NMI backtrace support
  *