KDE Plasma and GTK3 window buttons on inactive windows

I’ve noticed slightly annoying issue - I use GTK3 theme that changes gtk app window buttons when the window is not active. On Gnome it works as it should. Sadly on KDE Plasma it does not - the buttons stay the same no matter window is active or inactive. Is there a way to fix it?

It’s a minor thing but a bit annoying. Fading those buttons on inactive windows make things quite a bit more readable. Otherwise quite happy with the progress on setting up KDE for my needs - just need to squash / workaround the minor annoyances that are left.

Have you set the theme for GTK apps in the desktop setting?

Since you do not mention the theme in original post it is hard to test.

it is Sierra dark solid thin.
https://i.imgur.com/ZiiE8xc.png

Tried it under Gnome and there inactive window buttons get white. Would match Breeze Sierra KDE window decoration theme nicely.