Validate enums in variables

[vektah]

validation isn't firing when posting an enum value in a variable:

query = mutation setState($state: State!) {
    setState(state: $state) { id }
}

variables = {"state": "INVALID_STATE"}

results in

"errors": []

should be something like

   errors: [
    {
      "message": "Argument \"state\" has invalid value {state: INVALID_STATE}.\nIn field \"state\": Expected type \"State\", found INVALID_STATE.",
      "locations": [
        {
          "line": 14,
          "column": 22
        }
      ]
    }
  ]