How to fix Gulp.js "Error: path must be a string"

gulpfile.js: ```javascript ... browserify({ entries: [ './app/index.js' ], extensions: [ '.js', '.jsx' ], debug: true // Add sourcemaps }) .transform(babelify()) // JSX and ES6 => JS ... ``` A close-up of the issue: ```javascript .transform(babelify()) // JSX and ES6 => JS ``` The solution: ```javascript .transform(babelify) // JSX and ES6 => JS ```