swagger ui adds extra quotes when form submitted as multipart/form-data

Demonstration API definition

swagger: '2.0'
info:
  version: 0.0.0
  title: Simple API
host: 'localhost'
paths:
  /user/register:
    post:
      consumes:
        - "multipart/form-data"
      parameters:
        - in: "formData"
          name: "username"
          required: false
          type: "string"
          allowEmptyValue: false
        - in: "formData"
          name: "image"
          description: "User image"
          required: false
          type: "file"
        - in: "formData"
          name: "gender"
          description: "Gender: {male: 1, female: 2}"
          required: false
          items:  
            type: "string"
            allowEmptyValue: false
            enum:
              - "2"
              - "1"
          type: "array"
          allowEmptyValue: false

When I submit this form I see this curl command below response section:

curl -X POST "http://localhost/user/register" -H  "accept: application/json" -H  "Content-Type: multipart/form-data" -F "username=john" -F "gender="2""

Please note "gender="2"" <- extra quotes here

On the backend side submitted form always invalid because these extra quotes. If I change consumes to application/x-www-form-urlencoded then everything is fine but I can not upload image in that case.

What do I do wrong?

Reproduce the issue in Swagger UI 3.9.2 using the provided Swagger 2.0 definition and multipart/form-data submission. Start by tracing how the form parameters are serialized into the displayed curl command. Done means the gender value is emitted without extra quotes while file upload continues to work, with a regression test covering the case.