JSONSerialization formatting of Double

Hi,

I encountered a formatting problem during serialization of an object to JSON. Example code is

do {
  let double = Double(1.23)
  print(double)
  let json = try JSONSerialization.data(withJSONObject: ["double" : double])
  print(String(data: json, encoding: .utf8)!)
} catch {
  print(error.localizedDescription)
}

and the printed result on the command line is

1.23
{"double":1,23}

So directly printing the double value uses a "." as decimal point (wanted behavior) but serialized to JSON it is using a ",". To make it even more confusing, if I debug the code within Xcode I am getting a "." decimal point for JSON too.

I tried changing the Locale in code, setting system settings to "." as decimal point, … all to no avail. Does anyone have an idea?