What is missing to make my cascading DropDownList work

What is missing to make my cascading DropDownList work

Very easy case displayed here: http://jsbin.com/ahoYoPi/3/edit
I need to specify that the child's inner field to filter (eq) against the
parent's value field is "category_id"... Of course, Kendo's documentation
doesn't say anything about how to do that... Or is it something so super
obvious it doesn't deserve to be explained ?
var categoriesList = new Array (
{"id":"1","categoryName":"Fruits"},
{"id":"2","categoryName":"Vegetables"} );
var productsList = new Array(
{"id":"1","categorie_id":"1","productName":"Apples"},
{"id":"2","categorie_id":"1","productName":"Oranges"},
{"id":"3","categorie_id":"2","productName":"Carottes"},
{"id":"4","categorie_id":"2","productName":"Patatoes"});
$("#categories").kendoDropDownList({
dataTextField: "categoryName",
dataValueField: "id",
dataSource: categoriesList,
optionLabel: "----------------" ,
change: function() {
$("#products").data("kendoDropDownList").value(0);
}
});
$("#products").kendoDropDownList({
cascadeFrom: "categories",
dataTextField: "productName",
dataValueField: "id",
dataSource: productsList,
optionLabel: "----------------" ,
});