Dock widget with custom title widget is hard to manipulate

Creating a dock widget and assigning a custom widget using QDockWidget::setTitleBarWidget works fine. But trying to move the dock and put it floating is really hard after that. Moving and de-floating operations are also very hard then. The dock widget contents and title bar widget are painted correctly, but the dock widget frame is not painted.

Code to reproduce:
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#include <QtGui>

int main( int argc, char * argv[] )
{
QApplication app( argc, argv );
QMainWindow window;
QWidget central;
window.setCentralWidget( & central );
QVBoxLayout layout;
central.setLayout( & layout );
QTextEdit text1;
layout.addWidget( & text1 );
QDockWidget dock;
window.addDockWidget( Qt::RightDockWidgetArea, & dock );
QTextEdit text2;
dock.setWidget( & text2 );
QTextEdit text3;
dock.setTitleBarWidget( & text3 );
window.show();
return app.exec();
}
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