Redux concurrency problem

Program.cs

using System;
using Redux;
using System.Threading;
using System.Diagnostics;

namespace ReduxRaceCondition
{
    class MainClass
    {
        public class AddAction : IAction
        {
            public int Value { get; }
            public AddAction(int value)
            {
                Value = value;
            }
        }

        public static class Reducers
        {
            public static int MainReducer(int state, IAction action)
            {
                var act = action as AddAction;
                return state += (act.Value);
            }
        }

        public static void Main(string[] args)
        {
            var store = new Store<int>(Reducers.MainReducer, 0);
            int previous = -1;

            var thread1 = new Thread(() =>
            {
                for (int i = 0; i < 50000; ++i)
                {

                    store.Dispatch(new AddAction(1));
                    Thread.Sleep(3);
                }
            });

            var thread2 = new Thread(() =>
            {
                for (int i = 0; i < 50000; ++i)
                {
                    store.Dispatch(new AddAction(1));
                    Thread.Sleep(3);

                }
            });

            store.Subscribe(s =>
            {
                if (s < previous)
                {
                    Debugger.Break();
                }
                previous = s;
                Console.WriteLine(s);
            });

            thread2.Start();
            thread1.Start();

            Console.ReadKey();
        }
    }
}