Qt CSS :!hover seems to override defaults

[Huulivoide]

Qt version: 5.4.2

I am trying to style certain elements of my application with the CSS support.
I want the elements to look "normal" when they are active (:focus), but have
different styling when they are inactive . For this I need to use the :!focus selector,
but it results in the normal/default style not being applied to the widget when
focus is gained, instead the :!focus rules still persist. Adding another rule :focus
does override the :!focus, but I want to use the system's style's default instead
of my own values.

The small app below demonstrates problem with Qlabels and :!hover, which has
the same problem as the :!focus selector.

CssTest.pro:

QT += core gui widgets
SOURCES += CssTest.cpp

CssTest.cpp:

#include <QApplication>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);

    QVBoxLayout *mainLayout = new QVBoxLayout;

    QLabel* redLabel = new QLabel("Red when mouse does not hover over this,\n"
                                  "but should turn back to default color (black)\n"
                                  "when mouse hovers over this text.");
    redLabel->setStyleSheet("QLabel:!hover { color: red; }");
    mainLayout->addWidget(redLabel);

    QLabel* blueLabel = new QLabel("Black when mouse does not hover over this,\n"
                                   "but should turn to blue when the mouse hovers\n"
                                   "over this text.");
    blueLabel->setStyleSheet("QLabel:hover { color: blue; }");
    mainLayout->addWidget(blueLabel);

    QWidget *w = new QWidget();
    w->setLayout(mainLayout);
    w->setWindowTitle("Css negation");

    w->show();
    return app.exec();
}