Searching when parent term id is given

Hi, to make my issue apparent, here is an real world example:

- I have parent term called Fishing and a child term fishing lures.
- In order to search, I created a Index view and created added contextual filter (Content datasource: Categories » Taxonomy term » Term ID)

It works fine if I give child term id, however when parent term id is given, it loads nothing (since it doesn't search deeper child term levels?).

In D7 it seems that it was possible to check "Index Hierarchy" somewhere in settings, but I see no such an option in D8.

P.S. I also had this posted as Drupal Stackexchange's question: http://drupal.stackexchange.com/questions/212500/search-api-displays-chi...