Error message "isValid is not defined" after upgrade to Knockout.Validation 2.0.3

[verheyenkoen]

I just upgraded Knockout.Validation to the latest release (as I need validation on the new textInput binding) and on this existing binding:

<form data-bind="with: new">
    ....
    <button data-bind="enable: isValid, click: $parent.submit">Submit</button> // or isValid()
</form>

... the following error occurs:

Message: Unable to process binding "enable: function(){return isValid() }"
Message: isValid is not defined
    at enable (eval at createBindingsStringEvaluator (knockout-3.4.2.debug.js:2992), <anonymous>:3:59)
    at update (knockout-3.4.2.debug.js:4211)
    at ko.dependentObservable.disposeWhenNodeIsRemoved (knockout-3.4.2.debug.js:3383)
    at Function.evaluateImmediate_CallReadThenEndDependencyDetection (knockout-3.4.2.debug.js:2183)
    at Function.evaluateImmediate_CallReadWithDependencyDetection (knockout-3.4.2.debug.js:2150)
    at Function.evaluateImmediate (knockout-3.4.2.debug.js:2111)
    at Object.ko.computed.ko.dependentObservable (knockout-3.4.2.debug.js:1964)
    at knockout-3.4.2.debug.js:3381
    at Object.arrayForEach (knockout-3.4.2.debug.js:159)
    at applyBindingsToNodeInternal (knockout-3.4.2.debug.js:3353)

Basically I do this (heavily reduced code):

model.new = new MyModel();
ko.validatedObservable(model.new);
ko.applyBindings(model);

I also tried it like this, but the same error occurs:

model.new = ko.validatedObservable(new MyModel());
ko.applyBindings(model);

The strange thing is that if I change the button binding as follows, the error is gone, but the button remains disabled even if my model becomes valid:

<button data-bind="enable: $parent.new.isValid, click: submit">Submit</button>

I also checked in the console and executing model.new.isValid() there throws the error "Uncaught TypeError: model.new.isValid is not a function".

I guess something must have changed in either Knockout or Knockout validation but I can't find what could be wrong here.