How to format bad request error when whole request could not be parsed because of invalid enum?

Question

My request has enum property (enum FrontendId { Frontend1, Frontend2 }) and when invalid value is passed in that property I get following 400 response (for example if I pass {"frontendId": "invalid"}):

{
  "request": [
    "The request field is required."
  ],
  "$.frontendId": [
    "The JSON value could not be converted to Api.Models.ClientApi.LoginStart.LoginStartRequest. Path: $.frontendId | LineNumber: 1 | BytePositionInLine: 27."
  ]
}

But when I add custom Fluent validator for request to just for example whitlist some enum values and pass valid enum value in request then I get 400 response in normal format (for example if I pass {"frontendId": "Frontend2"}, which is not whitelisted):

{
  "FrontendId": [
    "The specified condition was not met for 'Frontend Id'."
  ]
}

In other words - when request can not be parsed because of invalid enum value then strange response is returned with request and $.frontendId keys. How I can fix this to not include "request" and have "FrontendId" instead of "$.frontendId"?