IE6 does not call jsonpCallback

j.ajax({
    type: 'GET',
    url: 'http://url',
    dataType: 'jsonp',
    jsonpCallback: 'mypkg.myfunc',开发者_如何学JAVA
    cache: true
})

For some reason the above code does not call the JsonCallback in case of IE6. For all other browsers, it works fine.