PUT request using WebAction.Request

I've been trying to setup a simple PUT request to an API with no success. The API itself works as intended, used Postman to request the data. GET/POST requests are working fine with PowerQuery.

let

  BaseUrl = "https://stackoverflow-63122537.herokuapp.com/demo"
  BaseHeaders = [#"Content-Type"="application/json"],
  JsonBody = Json.FromValue([A = 1, B = 2]),

  Count = 
    WebAction.Request(
      "PUT",
      BaseUrl,
        [
          Headers = [ BaseHeaders ],
          Content = JsonBody
        ]
    )
  
in
  Count

Expected:

Count should return a number.

Actual result:

PowerBI reports "Object reference not set to an instance of an object"