Why is TinyIoC is disposing of this instance?

gistfile1.cs

/*
install-package raven.database
install-package xunit
install-package nancy.testing
install-package shouldly
install-package nbuilder
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using CsQuery.Utility;
using FizzWare.NBuilder;
using Nancy;
using Raven.Client;
using Raven.Client.Document;
using Raven.Client.Embedded;
using Shouldly;
using Xunit;

namespace ConsoleApplication4
{
    public class SampleModule : NancyModule
    {
        private readonly IDocumentStore _documentStore;

        public SampleModule(IDocumentStore documentStore) : base("/")
        {
            _documentStore = documentStore;

            Get["/"] = _ => "Hello World";
        }
    }

    public class SampleRepo
    {
        [Fact]
        public async Task DoTest()
        {
            // Arrange.
            var documentStore = new EmbeddableDocumentStore
            {
                RunInMemory = true,
                Conventions = new DocumentConvention
                {
                    DefaultQueryingConsistency = ConsistencyOptions.AlwaysWaitForNonStaleResultsAsOfLastWrite
                }
            };
            documentStore.Initialize();
            using (var session = documentStore.OpenAsyncSession())
            {
                foreach (var item in Builder<FakeData>.CreateListOfSize(1000).Build())
                {
                    await session.StoreAsync(item);
                }

                await session.SaveChangesAsync();
            }

            var browser = new Nancy.Testing.Browser(with =>
            {
                with.Module<SampleModule>();
                with.Dependency<IDocumentStore>(documentStore); // EXCEPTION
                //with.Dependency(documentStore); // WORKS
            });

            using (var session2 = documentStore.OpenAsyncSession())
            {
                var foo = await session2.LoadAsync<FakeData>("fakeDatas/1");
            }

            // Act.
            var result = browser.Get("/");

            // Assert.
            result.StatusCode.ShouldBe(HttpStatusCode.OK);
        }
    }

    public class FakeData
    {
        public string Id { get; set; }
        public string Name { get; set; }
    }
}