Best practice - Where to put my class constants

Does anyone know why Kotlin does not allow private const val in a class like:

 class ThingDoer {
     private const val TAG = "Thing"

     fun doThing() { Log.i(TAG, "hello") }
 }

To me the JVM bytecode generated by Kotlin for both #1 and #2 isn’t optimal. I find it odd that this relatively common need isn’t resolved nicely / cleanly as I see it.

Any clues why this is the case?

Thanks, Rob.