webpack-scss-sass-file does not work with conditional css extract

I am using WEBPACKEXTRACT-PLUGIN to extract scss into css file.

Having trouble with conditional extract. At moment we have OLD-SCSS and NEW-SCSS so in my app.js file am doing like this.

if (somecondition) {
  require('path-to-old.scss');
} 
else {
  require('path-to-new.scss');
}

But the end result is coming combination of both OLD-SCSS and NEW-SCSS regardless of condition is true or false.

Is there any way to make it extract conditionally.