includePaths: require('node-normalize-scss').includePaths

var gulp = require('gulp');
var sass = require('gulp-sass');
 
gulp.task('sass', function () {
  gulp.src('path/to/input.scss')
    .pipe(sass({
      // includePaths: require('node-normalize-scss').with('other/path', 'another/path') 
      // - or - 
      includePaths: require('node-normalize-scss').includePaths
    }))
    .pipe(gulp.dest('path/to/output.css'));
});