Incorrect lengths reported by QTextDocument::contentsChange when pasting and clearing

#include <QApplication>
#include <QPlainTextEdit>
#include <QPushButton>
#include <QTextStream>
#include <QVBoxLayout>

class Widget : public QWidget
{
        Q_OBJECT
public:
        Widget(QWidget* parent = 0) : QWidget(parent)
        {
                mTextEdit = new QPlainTextEdit(this);
                mClearButton = new QPushButton("Clear", this);
                setLayout(new QVBoxLayout());
                layout()->addWidget(mTextEdit);
                layout()->addWidget(mClearButton);
                connect(mTextEdit->document(), SIGNAL(contentsChange(int,int,int)), this, SLOT(slotContentsChange(int,int,int)));
                connect(mClearButton, SIGNAL(clicked()), mTextEdit, SLOT(clear()));
        }
private slots:
        void slotContentsChange(int pos, int removed, int added)
        {
                QTextStream(stdout) << "pos: " << pos << ", removed: " << removed << ", added: " << added << endl;
        }
private:
        QPlainTextEdit* mTextEdit;
        QPushButton* mClearButton;
};

int main(int argc, char* argv[])
{
        QApplication app(argc, argv);
        Widget widget;
        widget.show();
        return app.exec();
}

#include "moc_test.cpp"