Gulp UnCSS ignore regex for bootstrap modal

gistfile1.txt

gulp.task('uncss', () => {
  return gulp.src([
      'dist/styles/main.css'
    ])
    .pipe(uncss({
      html: [
        'http://localhost:9000/'
      ],
      ignore: [ /\.modal/]
    }))
    .pipe(gulp.dest('dist/styles/uncss/'));
});