Using IActionResult with Azure Functions in .NET 5?

After migrating my Azure Functions project to .NET 5, it has started wrapping my responses in a weird wrapper class.

For instance, consider the following endpoint:

public record Response(string SomeValue);

[Function("Get")]
public async Task<IActionResult> Get(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "get-something")]
    HttpRequestData request)
{
    return new OkObjectResult(new Response("hello world"));
}

Before, it would return:

{
    "someValue": "hello world"
}

But now, it returns:

{
  "Value": {
    "SomeValue": "hello world"
  },
  "Formatters": [],
  "ContentTypes": [],
  "DeclaredType": null,
  "StatusCode": 200
}

I get that it must be because it just tries to serialize the object result, but I can't find any documentation on how this is supposed to work in .NET 5.

My main function currently looks like this:

public static async Task Main()
{
    var host = new HostBuilder()
        .ConfigureFunctionsWorkerDefaults(x => 
            x.UseDefaultWorkerMiddleware())
        .ConfigureAppConfiguration((_, builder) => builder
            .AddJsonFile("local.settings.json", true)
            .Build())
        .ConfigureServices(ConfigureServices)
        .Build();

    await host.RunAsync();
}

My project is located here, in case someone are interested: https://github.com/sponsorkit/sponsorkit.io

Currently, my .NET 5 work is on a branch called feature/signup-flow.