How to set focus on tabs button

[RadChand]

Hi!
I have to specify order of passage buttons in TabView including its header (buttons on tab bar).
If I don't use KeyNavigation I can navigate (by Tab key) through my buttons (b11, b12) and header of TabView (tab1, tab2, tab3).
But, if I use KeyNavigation I can navigate only through buttons (b11, b12).
How to specify tab bar in KeyNavigation.tab: ??? (I try set 'tab' and 'tabView' - doesn't work.)
Is there another way to set focus on header of TabView?

Build with Desktop Qt 5.7.0 MSVC2015 32bit

import QtQuick 2.7
import QtQuick.Window 2.2
import QtQuick.Layouts 1.1
import QtQuick.Controls 1.4
import QtQuick.Controls.Styles 1.2

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    TabView {
        id: tabView
        anchors.fill: parent
        Tab {
            id: tab1
            title: 'tab1'
            Row {
                Button { id: b11; text: 'b11'; KeyNavigation.tab: b12 }
                Button { id: b12; text: 'b12'; KeyNavigation.tab: tabView /*tab1*/}
            }
        }
        Tab { title: 'tab2'; Button { text: 'b21' } }
        Tab { title: 'tab3'; Button { text: 'b31' } }
    }
}

---

Andrew

[RadChand]

I've found a back door ))
TabBar is first child of TabView

KeyNavigation.tab: tabView.children[0] // it works