Line chart with two numeric axes

[flagg19]

What i have:

    var store=new Ext.data.JsonStore({fields:["x","y"],data:[
    {"x":6,"y":1},
    {"x":7,"y":2},
    {"x":10,"y":5}]});

        axes:[{
        type:"Numeric",
        position:"left",
        fields:["y"],
        title:"test_y",
        grid:1
    },
    {
        type:"Numeric",
        position:"bottom",
        fields:["x"],
        title:"test_x",
        grid:1
    }]

        series:[{type:"line",axis:"left",xField:"x",yField:"y"}]

Screen Shot 2012-05-29 at 3.10.41 PM.png

The problem:
First and last points are ok, but the one that should be at x=7 y=2 appear in x=8 y=2.
It's like all the points on the x axis that are between the first and the last points are calculated to have the same distance from each others. This behavior is almost like the one you have with a Category axis, I don't understand if I'm doing something wrong or a chart with two "real" numeric axes is not supported.
Every exemple I've found only use one numeric axis...

Thanks.