qt4: telx spinbutton doesn't update teletext page after pressing enter

The telx spin button doesn't update the teletext page when entering a new page number and pressing 'enter'. It only does that when clicking on the up and down arrows.

For instance when someone wants to jump to teletext page 888 and types this in the spinbutton number area. Then one will press enter the key on his keyboard. The qt4 user interface doesn't notify the telx/zvbi plugin of the teletext page change. Only when the user uses the up and down arrow the page will be selected.