Making NameSuggestionProvider work

I was trying custom implementation of Name suggestion provider, but it doesn't seem to get even initialized. 

class CustomNameSuggestionProvider : NameSuggestionProvider {
  init {
    println("Name Suggestion Provider initialized")
  }

  override fun getSuggestedNames(
    element: PsiElement, p1: PsiElement?, result: MutableSet<String>)
    : SuggestedNameInfo? {
    result.addAll(listOf("suggestion1", "suggestion2",))
    return null
  }

}

 I registered it like this within extensions like rest of providers that work:

<nameSuggestionProvider implementation="jarek.plugin.CustomNameSuggestionProvider">

The code however doesn't trigger, I tried to test this on test Kotlin file within ide on ‘introduce variable’ refactoring and nothing happens, not that I expected it to work as init block of plugin does't run after all.

Is there any extra step to make this Provider load? For instance associating it with particular language?