Klaxon Parse null

I have issue when using Klaxon 5.5

Class :

data class QRResponse(
   val qrType: String? = null,

   val qrData: String? = null

Code :

val dataContents = result.contents
Log.d("ScanQRData", "result.contents : $dataContents")

val dataQR = Klaxon().parse<QRResponse>(dataContents)
Log.d("ScanQRData", "dataQR : $dataQR")

Result :

ScanQRData: result.contents : {“qrType”: “product”, “qrData”:“352307811”}

ScanQRData: dataQR : QRResponse(qrType=null, qrData=null)

Any suggestion what happened to qrType and qrData null after parse from Klaxon?