gulp plumber async not working

gulp.js

var gulp = require('gulp');
var plumber = require('gulp-plumber');
var logger = require('winston');
var File = require('vinyl');
var Readable = require('stream').Readable;
var Writable = require('stream').Writable;
var Transform = require('stream').Transform;
var util = require('util')

/**
 * Gulp sample plugin
 * @return {[type]} [description]
 */
var plugin = function () {
	/**
	 * @class FileTransform
	 * @param {[type]} files [description]
	 */
	function FileTransform () {
		Transform.call(this, {objectMode: true})
	}
	util.inherits(FileTransform, Transform);

	FileTransform.prototype._transform = function (file, enc, cb) {
		logger.info('Running plugin on file', file.path)
		var self = this;
		setTimeout(function () {
			if (file.path == '/file5.tmp') {
				cb(new Error('simulated error'))
			} else {
				cb(null, file);	
			}			
		}, 100)
	}

	return new FileTransform();
}

/**
 * @class FileSource
 * @param {[type]} files [description]
 */
function FileSource (files) {
	Readable.call(this, {objectMode: true})
	this._files = files;
}
util.inherits(FileSource, Readable);

FileSource.prototype._read = function () {
	this.push(this._files.shift());
	if (this._files.length == 0)
		this.push(null)
}

/**
 * @class FileDest
 */
function FileDest () {
	Writable.call(this, {objectMode: true})
	this._files = [];
}
util.inherits(FileDest, Writable);

FileDest.prototype._write = function (file, enc, cb) {
	logger.info('Received file', file.path)
	this._files.push(file);
	cb(null)
}

gulp.task('test', function(cb) {
	var files = [
		new File({path: '/file1.tmp'}),
		new File({path: '/file2.tmp'}),
		new File({path: '/file3.tmp'}),
		new File({path: '/file4.tmp'}),
		new File({path: '/file5.tmp'}),
		new File({path: '/file6.tmp'}),	
		new File({path: '/file7.tmp'}),
		new File({path: '/file8.tmp'}),
		new File({path: '/file9.tmp'}),
		new File({path: '/file10.tmp'}),
	]
	var input = new FileSource(files);
	var output = new FileDest();

	var pipeline = input
		.pipe(plumber({}))
		.pipe(plugin())
		.pipe(output)
		.on('finish', function () {
			logger.info('end');
		})

	return pipeline;
});

gulp.start('test');

output.log

info: Running plugin on file /file1.tmp
info: Received file /file1.tmp
info: Running plugin on file /file2.tmp
info: Received file /file2.tmp
info: Running plugin on file /file3.tmp
info: Received file /file3.tmp
info: Running plugin on file /file4.tmp
info: Received file /file4.tmp
info: Running plugin on file /file5.tmp
[16:08:02] Plumber found unhandled error:
 Error: simulated error

package.json

{
  "dependencies": {
    "gulp": "^3.8.11",
    "gulp-plumber": "^1.0.1",
    "vinyl": "^0.4.6",
    "winston": "^1.0.0"
  }
}