QFileSystemModel does not update when the contents of a file changes (file size)

When I create new files, QFileSystemModel picks up the changes (touch NewFile). However if I change the contents of a file, the view does not get updated (echo "foobar" > NewFile).

The QFileSystemWatcher does not emit the directoryChanged signal when a file has been modified. The documentation reads: "This signal is emitted when the directory at a specified path, is modified (e.g., when a file is added, modified or deleted) or removed from disk."

Test case main.cpp to reproduce issue
====================================
#include <QtGui>

class TreeView : public QTreeView
{
Q_OBJECT
public:
TreeView(QWidget *parent = NULL) : QTreeView(parent)

{ QFileSystemModel *model = new QFileSystemModel(this);; model->setRootPath("/"); setModel(model); setRootIndex(model->index(QDir::currentPath())); }

};

#include "main.moc"

int main(int argc, char **argv)
{
QApplication a(argc, argv);
TreeView w;
w.show();
return a.exec();
}