vectorMap deselecting selected regions

Question

I'm trying to clear the user-selected region on click. But the selected region won't deselect. You can toggle empty or not selected but if you have predefined some regions then I can't find a solution to deselect it. onRegionClick detects a click, but I have no idea how to deselect.

Here is my code:

$('#worldMap').vectorMap({
    onRegionTipShow: function(event, label, code)
    {
       label.html(label.html()+' <img src="'+getFlagImgSrc(code)+'" height="12">');
    },
    onRegionClick: function(event, code) {
        console.log(code);
    },
    regionsSelectable: true,
    map: 'world_mill',
    backgroundColor: "transparent",
    zoomOnScroll: true,
    regionStyle: {
    selected: {
        fill: '#999999'
    },
    initial: {
        fill: '#e4e4e4',
        "fill-opacity": 0.9,
        stroke: 'none',
        "stroke-width": 0,
        "stroke-opacity": 0
    }
},
series: {
    regions: [{
        values: mapData,
        scale: ["#AAAAAA", "#999999"],
        normalizeFunction: 'polynomial'
    }]
});