Why notification use the res of mipmap as smallIcon will crash system ui in Android O?

Question

If I use the mipmap icon as smallIcon of a Notification in Android O, when notify it, the system ui will crash. But it works below O, and if I change the icon with res in drawable directory, it works as well. Although Google tell us we should place our app icons in mipmap dirs, why I can not use it as the notification icon in Android O?

NotificationCompat.Builder notificationBuilder =
            new NotificationCompat.Builder(this, channelId)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle(notification.getTitle())
                .setContentText(notification.getBody())
                .setAutoCancel(true)
                .setDefaults(Notification.DEFAULT_ALL)
                .setContentIntent(pendingIntent);