Почему не срабатывает gulp watch?

var gulp        = require('gulp'),
    less        = require('gulp-less'),
    browserSync = require('browser-sync');
    
gulp.task('less', function() {
    return gulp.src('app/less/**/*.less')
        .pipe(less())
        .pipe(gulp.dest('app/css'))
        .pipe(browserSync.reload({stream: true}))
});

gulp.task('browser-sync', function() {
    browserSync({
        server: {
            baseDir: 'app'
        },
        notify: false
    });
});

gulp.task('watch', ['browser-sync', 'less'], function() {
    gulp.watch('app/less/**/*.less', gulp.parallel('less'));

});

C:\Users\rybak\Desktop\rybakooov.github.io\lazer-cosm>gulp watch
assert.js:351
throw err;
^

AssertionError [ERR_ASSERTION]: Task function must be specified
at Gulp.set [as _setTask] (C:\Users\rybak\Desktop\rybakooov.github.io\lazer-cosm\node_modules\undertaker\lib\set-task.js:10:3)
at Gulp.task (C:\Users\rybak\Desktop\rybakooov.github.io\lazer-cosm\node_modules\undertaker\lib\task.js:13:8)
at Object. (C:\Users\rybak\Desktop\rybakooov.github.io\lazer-cosm\gulpfile.js:21:6)
at Module._compile (internal/modules/cjs/loader.js:738:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:749:10)
at Module.load (internal/modules/cjs/loader.js:630:32)
at tryModuleLoad (internal/modules/cjs/loader.js:570:12)
at Function.Module._load (internal/modules/cjs/loader.js:562:3)
at Module.require (internal/modules/cjs/loader.js:667:17)
at require (internal/modules/cjs/helpers.js:20:18)