UserProperties not passed to client

[rofr]

I'm intercepting messages on a custom server and want to attach some metadata before passing on to clients. Here is my interceptor:

    private static async Task OnMessagePublished(InterceptingPublishEventArgs a)
    {
        Console.WriteLine("message received");
        var topic = a.ApplicationMessage.Topic;
        var payload = a.ApplicationMessage.ConvertPayloadToString();

        Console.WriteLine("payload:" + payload);
        var recordNumber = await Store.Append(topic, payload);
        
        Console.WriteLine("recordNumber: " + recordNumber);
        a.ApplicationMessage.UserProperties = new()
        {
            new("RecordNumber", recordNumber.ToString())
        };
    }

And on my custom client I want to retrieve the UserProperties but the collection is null:

    private static async Task MessageReceived(MqttApplicationMessageReceivedEventArgs arg)
    {
        var message = arg.ApplicationMessage;
        var payload = message.ConvertPayloadToString();
        Console.WriteLine("Message received, payload: " + payload);
        Console.WriteLine("UserProperties is null: " + (message.UserProperties is null));
        Console.WriteLine("Record number:" + message.UserProperties.Where(p => p.Name == "RecordNumber").Select(p => p.Value));
        await arg.AcknowledgeAsync(CancellationToken.None);
    }

What am I missing? This is NET6 and version 4.1.2.350

[chkr1011]

Did you set the protocol version to 5.0.0 in the client options?

[rofr]

Thank you, that was an easy fix... I suspected it could be version related but didn't find the option late last night.