Adding an instance of QPrinter as a combo box's user data return None

class Window(QtGui.QMainWindow):

    def __init__(self):
        super(Window, self).__init__()

        self.combo = QtGui.QComboBox(self)

        self.setCentralWidget(self.combo)

        printer = QtGui.QPrinterInfo.availablePrinters()[0]

        self.combo.addItem(printer.printerName(), QtGui.QPrinter(printer))

        # Fails
        assert(isinstance(self.combo.itemData(0), QtGui.QPrinter))