Material Design Best Practice: Should a dialog "Accept" button only get enabled upon changes to a mutable inner state

As far as UX goes, particularly when working within the material design specifications for a Windows app, if an accept/cancel dialog is presented to the user that is intended to mutate some "model" or save some data, should the button intended to save changes only get enabled once changes have been made? (forcing them to use cancel if no changes performed)

Or is it better to have the save button enabled by default on dialog open? (disabling it if validation fails of course)

To be clear, this is a dialog, and both buttons immediately close the dialog and perform the save action.