GULP - erro Task function must be specified

const gulp = require('gulp'); const sass = require('gulp-sass'); const paths = require('./gulp-paths.json'); const concat = require('gulp-concat');

var sassDevOptions = { outputStyle: 'expanded' }

var sassProdOptions = { outputStyle: 'compressed' }

gulp.task('sass', function() { return gulp.src( paths.src.css.all ) .pipe(sass(sassProdOptions).on('error', sass.logError)) .pipe(concat('bundle.min.css')) .pipe(gulp.dest( paths.dest.css )) });

gulp.task('watch', function(){ gulp.watch( paths.src.css.all , 'sass') });

gulp.task('default', ['watch', 'sass']);

---- Quando digito "gulp" no cmder, apresenta o seguinte erro:

C:\Users\Marcelo.Silva\Desktop\Novo Projeto\Mellow (src@1.0.0) λ gulp

assert.js:350 throw err; ^

AssertionError [ERR_ASSERTION]: Task function must be specified at Gulp.set [as setTask] (C:\Users\Marcelo.Silva\Desktop\Novo Projeto\Mellow\nodemodules\undertaker\lib\set-task.js:10:3) at Gulp.task (C:\Users\Marcelo.Silva\Desktop\Novo Projeto\Mellow\node_modules\undertaker\lib\task.js:13:8) at Object. (C:\Users\Marcelo.Silva\Desktop\Novo Projeto\Mellow\gulpfile.js:34:6) at Module.compile (internal/modules/cjs/loader.js:688:30) at Object.Module.extensions..js (internal/modules/cjs/loader.js:699:10) at Module.load (internal/modules/cjs/loader.js:598:32) at tryModuleLoad (internal/modules/cjs/loader.js:537:12) at Function.Module._load (internal/modules/cjs/loader.js:529:3) at Module.require (internal/modules/cjs/loader.js:636:17) at require (internal/modules/cjs/helpers.js:20:18)

Detalhe, todas dependências estação instaladas corretamente.