How to indicate a default button in Material Design

I'm creating a Windows desktop application with Material Design (using Material Design in XAML Toolkit), and I'm wondering how to indicate that a specific button is the default button (i.e. will be triggered if Enter is pressed anywhere in the form).

In normal Windows applications, the OK button is visibly highlighted to indicate this (see the top row in the following image from this question), but I can't find any mention in the Material Design guidelines (Dialogs), Buttons) of how the default button should be indicated (nor does the toolkit I'm using highlight default buttons in any way).