ApiVersionNeutral causes {version} parameter to show in swagger

Question

I've upgraded a project from .net core 3.1 to .net 8. I had to update packages from Microsoft.AspNetCore.Mvc.Versioning to Asp.Versioning.Mvc.

I use versioning in my routes:

[ApiController]
[ApiVersionNeutral]
[ApiConventionType(typeof(DefaultApiConventions))]
[Route("~/v{version:apiVersion}/[controller]")]
public class SampleController : ControllerBase
{
   [HttpGet("{userId}", Name = "GetUser")]
   public async Task<ActionResult<UserResponseModel>> GetUser([FromRoute] int userId)
   {
      // Do something
   }
}

The versioning worked fine before the upgrade, but afterwards {version} is now a parameter (seen in Swagger) /v{version}/GetUser/{userId}

If I change [ApiVersionNeutral] to [ApiVersion("1.0")] the endpoint is correct. /v1/GetUser/{userId}

My config has, and always had, the correct options:

services.AddApiVersioning(c =>
{
   c.ReportApiVersions = true;
   c.DefaultApiVersion = new ApiVersion(1, 0);
   c.AssumeDefaultVersionWhenUnspecified = true;
});

Any ides on why [ApiVersionNeutral] has this issue?

RESOLVED!

I found that I also need AddApiExplorer option AddApiVersionParametersWhenVersionNeutral = true