diff --git a/kernel/timer.c b/kernel/timer.c
index 308bc82..62c0618 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -102,7 +102,7 @@
 	_init_timeout(&timer->timeout, _timer_expiration_handler);
 	SYS_TRACING_OBJ_INIT(k_timer, timer);
 
-	timer->user_data = 0;
+	timer->user_data = NULL;
 }