Service doesn't get triggered after phone restart

I want to intercept when a sms has been received using:

[BroadcastReceiver(Enabled = true, Label = "SMS Receiver")]
    [Android.App.IntentFilter(new[] { "android.provider.Telephony.SMS_RECEIVED" })] 
    public class SmsReceiver:BroadcastReceiver
    {
        public override void OnReceive(Context context, Intent intent)
        {
              ...
        }   
    }

Everything works fine; except that if the phone is restarted it never gets triggered.

Any thoughts?