flutter secure storage not working ios code example

Example: secure storage flutter does not get removed on ios

import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:shared_preferences/shared_preferences.dart';

// ...

final prefs = await SharedPreferences.getInstance();

if (prefs.getBool('first_run') ?? true) {
  FlutterSecureStorage storage = FlutterSecureStorage();

  await storage.deleteAll();

  prefs.setBool('first_run', false);
}