How to fix datatable header in vuetify 2?

Question

Vue.js

Moved to 2nd vuetify, everything is cool.
I want the header in the datatable to be "glued" to the top and not disappear when the contents of the table are scrolled.
This was promised to be done just in the 2nd version - https://github.com/vuetifyjs/vuetify/issues/1547
An option appeared in the dock - fixed-header, but for some reason it does not work for me, the header still "leaves" .