Using deserialized instance's delegation throws NullPointerException

The following code throws NullPointerException. Is it expected behavior?

package sample

import kotlinx.serialization.Serializable
import kotlinx.serialization.json.JSON

interface IntId {
  var id: Int
}

interface IData {
  var msg: String?
}

@Serializable
data class Data(
  override var msg: String? = null
) : IData


@Serializable
data class IdData(
  override var id: Int,
  var data: Data
) : IntId, IData by data

inline fun <reified T : Any> deserialTest(root: T): T {
  val json = JSON.stringify(root)
  println(json)
  val obj = JSON.parse<T>(json)
  println(obj)
  return obj
}

fun main(args: Array<String>) {
  val src = IdData(3, Data("asdf"))
  val restored = deserialTest(src)
  println(restored.msg)
}

> Task :run FAILED
{"id":3,"data":{"msg":"asdf"}}
IdData(id=3, data=Data(msg=asdf))
Exception in thread "main" java.lang.NullPointerException
	at sample.IdData.getMsg(XSerialization.kt)
	at sample.XSerializationKt.main(XSerialization.kt:38)

[IARI]

Delegation does seem to work fine for me, if the Object is instantiated by default in the constructor:

@Serializable
class MyImpl(val base: BaseClass = BaseClass()) : BaseClass by base {
    ...
}

[NamekMaster]

Delegation does seem to work fine for me, if the Object is instantiated by default in the constructor:

@Serializable
class MyImpl(val base: BaseClass = BaseClass()) : BaseClass by base {
    ...
}

This is an accessible workaround for me, Thanks