AA_UseStyleSheetPropagationInWidgetStyles does not work if parent widget is already shown

Run the attached testcase and see red text "Test". This is correct as the style sheet is set to "QMainWindow { color: red }" and the red color propagates to the text.

Now click RMB and see "Test 2" but in black! It is expected to be red as the QLabel is child of QMainWindow and it should derive the palette.

What is interesting if you uncomment lines 26,27 (which set and reset some dummy sylesheet to the label) the label gets proper color:   

    ll->setStyleSheet("background-color: blue");
    ll->setStyleSheet("");