diff --git a/tools/testing/selftests/arm64/bti/test.c b/tools/testing/selftests/arm64/bti/test.c
index 656b04976ccc6389e03dd46f6b344c1217c41137..67b77ab83c20ed2098578c0ab14877b63259035a 100644
--- a/tools/testing/selftests/arm64/bti/test.c
+++ b/tools/testing/selftests/arm64/bti/test.c
@@ -6,6 +6,7 @@
 
 #include "system.h"
 
+#include <stddef.h>
 #include <linux/errno.h>
 #include <linux/auxvec.h>
 #include <linux/signal.h>