TypeError: Cannot read property 'on' of undefined

[resting]

I'm getting the error below when I include the postcss pipe.
Not sure what's wrong.

TypeError: Cannot read property 'on' of undefined
at DestroyableTransform.Readable.pipe (/node_modules/through2/node_modules/readable-stream/lib/_stream_readable.js:535:7)
at Gulp.<anonymous> (/gulpfile.js:9:10)
at module.exports (/node_modules/orchestrator/lib/runTask.js:34:7)
at Gulp.Orchestrator._runTask (/node_modules/orchestrator/index.js:273:3)
at Gulp.Orchestrator._runStep (/node_modules/orchestrator/index.js:214:10)
at Gulp.Orchestrator.start (/node_modules/orchestrator/index.js:134:8)
at /usr/local/lib/node_modules/gulp/bin/gulp.js:129:20
at _combinedTickCallback (node.js:370:9)
at process._tickCallback (node.js:401:11)
at Function.Module.runMain (module.js:449:11)

Heres the Gulpfile.js

var gulp = require('gulp'),
    sass = require('gulp-sass'),
    postcss = require('gulp-postcss'),
    autoprefixer = require('autoprefixer');

gulp.task('css', function () {
    return gulp.src('sass/style.scss')
        .pipe(sass().on('error', sass.logError))
        .pipe(postcss[autoprefixer({browsers: ['last 2 versions']})])
        .pipe(gulp.dest(''));
});

[TrySound]

I already answered you
postcss/postcss#766 (comment)
And you forgot parentheses after postcss word

[w0rm]

@resting can you set up a test project with a gulp task that I can run to reproduce the issue? The code looks fine to me (except the already mentioned missing parentheses). Also, which version of node do you use?

[resting]

I got .pipe(sass().on('error', sass.logError)) from https://github.com/dlmanning/gulp-sass#basic-usage. Its working on another system too. Listing node and gulp versions below:

Problematic
node: 5.8.0
gulp: 3.9.1

Working
node: 5.4.1
gulp: 3.9.1

@w0rm I don't mind setting up a test project. Do you just need package.json and gulpfile.js?

[resting]

Sorry guys, the solution is at postcss/postcss#766 (comment)
Was missing a parenthesis. Correct syntax below.

.pipe(postcss([
            autoprefixer({browsers: ['last 2 versions']})
        ]))

[w0rm]

@resting everyone mentioned the parenthesis, although I assumed it was just a typo :) glad that you figured this out.