Invalid output for First-Class JSON Types

Grape allows to define parameter as json and describe its structure: https://github.com/ruby-grape/grape#first-class-json-types. I was surprised to find out, that grape-swagger cannot handle it in the right way. The simplest example:

requires :json, type: JSON do
  requires :int, type: Integer, values: [1, 2, 3]
end

Parameter definitions in swagger output:

"parameters": [
  {
    "in": "formData",
    "name": "api_key",
    "type": "string",
    "required": true
  },
  {
    "in": "formData",
    "name": "json",
    "type": "json",
    "required": true
  },
  {
    "in": "formData",
    "name": "json[int]",
    "type": "integer",
    "format": "int32",
    "enum": [
      1,
      2,
      3
    ],
    "required": true
  }
]

That's what appears in documentation:

Start by reproducing the First-Class JSON Types example from the issue and inspect the generated Swagger parameter definitions. Trace how the nested JSON parameter and its int field are documented; done means the output represents the JSON structure correctly instead of exposing the nested field as a separate formData parameter.