Automatic deserialization $type failing test

FailingTest.cs

[Fact]
public void ShouldStoreAndRetrieveDictionary() {
    string id = null;
    using ( var session = _documentStore.OpenSession() ) {
        var doc = new Test() {
            Settings = new Dictionary<string, object>
            {
                    {"lastUsedUnitId", new Dictionary<int, string>()
                    {
                        {1, "units-3368"}
                    }}
                }
        };
        session.Store( doc );
        id = doc.Id;
        session.SaveChanges();
    }

    WaitForUserToContinueTheTest( _documentStore );

    using ( var session = _documentStore.OpenSession() ) {
        session.Advanced.DocumentStore.Operations.Send( new PatchOperation(
            id: id,
            changeVector: null,
            patch: new PatchRequest {
                Script = @"this.Settings[""lastUsedUnitId""] = {
                                ""1"": ""units-3982"",
                                ""$type"": ""System.Collections.Generic.Dictionary`2[[System.Int32, mscorlib],[System.String, mscorlib]], mscorlib""
                            };"
            },
            patchIfMissing: null ) );
    }


    using ( var session = _documentStore.OpenSession() ) {
        var result = session.Load<Test>(id);
        WaitForUserToContinueTheTest( _documentStore );
        Assert.True( result.Settings.TryGetValue( "lastUsedUnitId", out var dict ) );
        Assert.True( dict.GetType() == typeof( Dictionary<int, string> ) );
    }
}

private class Test {
    public string Id { get; set; }
    public Dictionary<string, object> Settings { get; set; }
}