settings QGridLayout spacing 0 causes QCheckBox and QLabel to overlap

#include <QtGui>

int main( int argc, char **argv )
{
  QApplication a(argc, argv);

  QCheckBox* w1 = new QCheckBox("When placed very closely");
  QLabel* w2 = new QLabel("labels begin to overlap with Qt/Carbon 4.7");
  QWidget* cntr = new QWidget();
QGridLayout* grid = new QGridLayout(cntr);
grid->addWidget(w1, 0,0);
grid->addWidget(w2, 0,1);
grid->setColumnStretch(2,1);
grid->setSpacing(0);

cntr->show();
a.exec();

return 0;
}