Accessing user set 2101

public class Plugin : IPlugin, IHttpRequestFilter
{
    private IUsers _usersService;

    public Task FilterRequest(IHttpRequest request)
    {
        Apis.Get<IEventLog>().Write($"access user: {_usersService.AccessingUser.Id}" , new EventLogEntryWriteOptions());

        return Task.CompletedTask;
    }

    public void Initialize()
    {
        _usersService = Apis.Get<IUsers>();
    }
}

Not sure what the problem is here, but it only ever returns the anonymous user account.