diff --git a/include/zephyr/sys/timeutil.h b/include/zephyr/sys/timeutil.h
index 3da7ccdd733..7c5db054f36 100644
--- a/include/zephyr/sys/timeutil.h
+++ b/include/zephyr/sys/timeutil.h
@@ -338,7 +338,7 @@ static inline bool timespec_is_valid(const struct timespec *ts)
 {
 	__ASSERT_NO_MSG(ts != NULL);
 
-	return (ts->tv_nsec >= 0) && (ts->tv_nsec < NSEC_PER_SEC);
+	return (ts->tv_nsec >= 0) && (ts->tv_nsec < (long)NSEC_PER_SEC);
 }
 
 /**