I have problem in windows app, not add class "wp"


I have a problem generating the app for windows.

When I run the “ionic build windows” command, add css “md” class instead of “wp” that causes the screens look bad.

Cordova CLI: 6.1.1
Gulp version: CLI version 3.9.1
Gulp local:
Ionic CLI Version: 2.1.0
Ionic App Lib Version: 2.1.0-beta.1
OS: Windows 10 x64
Node Version: v4.4.7

I hope you can help me.