Hiragana text painted over when setting stylesheet background to transparent

#include <QtGui>

class Foo : public QWidget {
public:
    Foo() : QWidget(0) {
        QVBoxLayout *lay = new QVBoxLayout(this);
        QTextEdit *textEdit = new QTextEdit;
        textEdit->setStyleSheet("background:transparent");
        lay->addWidget(textEdit);

    }
};

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

    QApplication app(argc, argv);

    Foo foo;
    foo.show();

    return app.exec();
}