Argument not passed to command handler?

So I have a .net core 3.1 console app, package version 2.0.0-beta1.20574.7 and this code:

```
using System;
using System.CommandLine;
using System.CommandLine.Invocation;
using System.Threading.Tasks;

namespace CommandParseTest
{
class Program
{
private static async Task Main(string[] args)
{
Console.WriteLine(Environment.CommandLine);
var realMain = new RootCommand("my program")
{
new Option(
"--x",
"Pass a number"
)
};

realMain.Handler = CommandHandler.Create(Run);
await realMain.InvokeAsync(args);
}

private static async Task Run(int foundItemFileToRead)
{
Console.WriteLine(foundItemFileToRead);
}
}
}
```

Now, if I call this like `CommandParseTest.exe --x 3`, I get 0.
Am I doing something wrong?