Android Kotlin Protected property exposes its private type ExpiresLayout

I converted my Java Activity class using Android Studio Kotlin plugin. Android Studio > Code > 'Converting Java code to Kotlin'

I am getting this error.

Error:(109, 19) 'protected (in Fragment)' property exposes its 'private' type ExpiresLayout

Code

protected val mExpiresLayout = ExpiresLayout.NORMAL

Any Idea? Thanks