Validating Data On A "previous" Button

I’ve been using the great “Yii Wizard Behaviors” extension and had a question.

I’ve noticed that when moving backward through a form (i.e. clicking on a previous button), the form state doesn’t save. I’m wondering if this is by design, however, if someone is just moving backwards to edit some information, they would lose all of the information that they were currently on if they hit a “previous” button.

Any ideas on what to do so that a step’s session state is saved when going backwards?