knockout dependentObservables do not trigger notifications

See https://groups.google.com/forum/#!topic/knockoutjs/bX8ze5S1w8o

HTML

<script src="https://github.com/downloads/SteveSanderson/knockout/knockout-1.2.1.js"></script>
<html>
    <body>
        Updates from 1 will not be shown in 2 because knockout dependentObservables do
        not tigger notifications on write. See <a target="_blank" href="https://groups.google.com/forum/#!topic/knockoutjs/bX8ze5S1w8o">discussion</a>.
        <hr/>
        Dependent Observable on testValue 1 <input type="text" data-bind="value: testDependantObservable" \>
        <br />
        Dependent Observable on testValue 2 <input type="text" data-bind="value: testDependantObservable" \>
        <br />
        Actual testValue<input id="actualTestValue" type="text"\>
    </body>
</html>

JavaScript

$(document).ready(function () {
    var testValue = 1;
    $("#actualTestValue").val(testValue);
    var viewModel = {
        testDependantObservable: ko.dependentObservable({
            read: function() {
                return testValue;
            },
            write: function (value) {
                testValue = value;
                $("#actualTestValue").val(testValue);
            }
        })
    }
    ko.applyBindings(viewModel);
});