Autorest does not generate the client with null values

[w4mhi]

I have the following section in swagger:

    "/api/configuration/person": {
      "get": {
        "tags": [
          "PersonInformation"
        ],
        "summary": " (Auth policies: Reader)",
        "operationId": "GetPersonInformation",
        "parameters": [
          {
            "name": "lastname",
            "in": "query",
            "description": "'lastname' is optional parameter.",
            "allowEmptyValue": true,
	        "required": false,
            "schema": {
              "type": "string",
              "nullable": true
            }
          },
          {
            "name": "api-version",
            "in": "query",
            "schema": {
              "type": "string"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": {
                    "$ref": "#/components/schemas/GetPersonInformation"
                  }
                }
              }
            }
          },
          "400": {
            "description": "Bad Request"
          },
          "404": {
            "description": "Not Found"
          },
          "500": {
            "description": "Server Error"
          }
        }
      }
    },

This swagger comes from the API definition:

[HttpGet]
[Authorize(Policy = "Reader")]
[Route("configuration/drops", Name = nameof(GetPersonInformation))]
[SwaggerResponse(StatusCodes.Status200OK, type: typeof(IEnumerable<PersonInformation>))]
[SwaggerResponse(StatusCodes.Status400BadRequest)]
[SwaggerResponse(StatusCodes.Status404NotFound)]
[SwaggerResponse(StatusCodes.Status500InternalServerError)]
    public async Task\<IActionResult\> GetPersonInformation(
        CancellationToken cancellationToken,
        string lastname = null)

I ran autorest with parameters:
autorest --input-file=swagger.json --csharp --add-credentials --verbose

AutoRest code generation utility \[cli version: 3.7.1; node: v18.18.0\]
(C) 2018 Microsoft Corporation.
https://aka.ms/autorest
info    | AutoRest core version selected from configuration: ^3.2.0.
info    |    Loading AutoRest core      '.autorest@autorestcore@3.9.7\nodemodules@autorest\core\dist' (3.9.7)

The result is this:

public virtual async Task\<Response\> GetPersonInformation(string lastname, RequestContext context)

I expected (in previous version was correctly generated):

public virtual async Task\<Response\> GetPersonInformation(string lastname = null, RequestContext context = null)

Does anyone have a suggestion? What am I missing? Thank you!