Why Kotlin modifier 'open' is incompatible with 'data'?

I have a class:

open data class Person(var name: String)

and another class:

data class Student(var reg: String) : Person("")

this gives me an error that:

error: modifier 'open' is incompatible with 'data'

if I remove data from Person class it's fine.

why kotlin open and data incompatible?