How to skip client validation on a empty optionnal field

I’m stucked on a problem and I don’t find any informations on Google or the forum. And I’m pretty sure I’m not the first one to have this limitation.

I have a ActiveForm with with the ClientValidation enabled.

Is there a way to skip the validation on an “optionnal” field that is null? I don’t want it to have the “has-success” class when empty.