diff --git a/.babelrc b/.babelrc
index cd6c919be..6f6f27bfe 100644
--- a/.babelrc
+++ b/.babelrc
@@ -11,6 +11,7 @@
     "resource/react.js",
     "resource/react-dom.js",
     "resource/bluebird.js",
+    "resource/bluebird/*.js",
     "test/resource/httpd.js",
     "test/resource/mocha.js",
     "test/resource/co-mocha.js"
diff --git a/gulp/babel-worker.js b/gulp/babel-worker.js
index 8d4899cbe..d77f01b1f 100644
--- a/gulp/babel-worker.js
+++ b/gulp/babel-worker.js
@@ -4,6 +4,7 @@
 const fs = require('fs');
 const path = require('path');
 const babel = require('babel-core');
+const minimatch = require('minimatch')
 const mkdirp = require('mkdirp');
 const options = JSON.parse(fs.readFileSync('.babelrc'));
 
@@ -11,35 +12,41 @@ const options = JSON.parse(fs.readFileSync('.babelrc'));
 onmessage = (ev) => {
 	const t1 = Date.now();
 	const sourcefile = path.normalize(ev.data);
-	let isError = false;
+	let error = null;
 	let isSkipped = false;
-	
+
 	fs.readFile(sourcefile, 'utf8', (err, data) => {
 		var transformed;
 		if(sourcefile === 'resource/react-dom.js') {
 			transformed = data.replace(/ownerDocument\.createElement\((.*?)\)/gi, 'ownerDocument.createElementNS(DOMNamespaces.html, $1)');
-		} else if('ignore' in options && options.ignore.includes(sourcefile)) {
+		} else if('ignore' in options && options.ignore.some(ignoreGlob => minimatch(sourcefile, ignoreGlob))) {
 			transformed = data;
 			isSkipped = true;
 		} else {
-			transformed = babel.transform(data, options).code;
+			try {
+				transformed = babel.transform(data, options).code;
+			} catch(c) {
+				transformed = data;
+				isSkipped = true;
+				error = c.message;
+			}
 		}
 
 		const outfile = path.join('build', sourcefile);
-		isError = !!err;
+		error = error || err;
 
 		mkdirp(path.dirname(outfile), err => {
-			isError = !!err;
+			error = error || err;
 
 			fs.writeFile(outfile, transformed, err => {
-				isError = !!err;
-				const t2 = Date.now();
+				error = error || err;
 
+				const t2 = Date.now();
 				postMessage({
-					isError,
 					isSkipped,
 					sourcefile,
 					outfile,
+					error,
 					processingTime: t2 - t1
 				});	
 			});
diff --git a/gulpfile.js b/gulpfile.js
index d22967a64..dc2c3426c 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -1,6 +1,5 @@
 'use strict';
 
-const path = require('path');
 const gulp = require('gulp');
 const del = require('del');
 const vfs = require('vinyl-fs');
@@ -12,15 +11,24 @@ const glob = require('glob');
 const Worker = require('tiny-worker');
 const merge = require('merge-stream');
 const tap = require('gulp-tap');
-const rename = require("gulp-rename");
+const rename = require('gulp-rename');
 const browserify = require('browserify');
 const reactPatcher = require('./gulp/gulp-react-patcher');
+const isWindows = /^win/.test(process.platform);
 const NODE_ENV = process.env.NODE_ENV;
+const workers = [];
+var isExiting = false;
 
 const formatDirsforMatcher = dirs => {
 	return dirs.length > 1 ? `{${dirs.join(',')}}` : dirs[0];
 };
 
+const killAllWorkers = () => {
+	for(let worker of workers) {
+		worker.terminate();
+	}
+};
+
 // list of folders from where .js files are compiled and non-js files are symlinked
 const dirs = [
 	'chrome',
@@ -72,16 +80,24 @@ const browserifyConfigs = [
 const jsGlob = `./\{${dirs.join(',')}\}/**/*.js`;
 const jsGlobIgnore = `./\{${symlinkDirs.concat(copyDirs).join(',')}\}/**/*.js`;
 
-function onError(err) {
-	gutil.log(gutil.colors.red('Error:'), err);
-	this.emit('end');
+function onError(shouldExit, err) {
+	if(shouldExit) {
+		isExiting = true;
+		killAllWorkers();
+		throw new Error(err);
+	} else {
+		gutil.log(gutil.colors.red('Error:'), err);
+		this.emit('end');
+	}
 }
 
 function onSuccess(msg) {
-	gutil.log(gutil.colors.green('Build:'), msg);
+	if(!isExiting) {
+		gutil.log(gutil.colors.green('Build:'), msg);
+	}
 }
 
-function getBrowserify() {
+function getBrowserify(exitOnError = true) {
 	const streams = browserifyConfigs.map(config => {
 		return gulp
 			.src(config.src)
@@ -89,39 +105,49 @@ function getBrowserify() {
 				file.contents = browserify(file.path, config.config).bundle();
 			}))
 			.pipe(rename(config.dest))
+			.on('error', function(err) { onError.bind(this)(exitOnError, err); })
+			.on('data', file => {
+				onSuccess(`[browserify] ${file.path}`);
+			})
 			.pipe(gulp.dest('build'));
 	});
 
 	return merge.apply(merge, streams);
 }
 
-function getJS(source, sourceIgnore) {
+function getJS(source, sourceIgnore, exitOnError = true) {
 	if (sourceIgnore) {
 		source = [source, '!' + sourceIgnore];
 	}
 
 	return gulp.src(source, { base: '.' })
 		.pipe(babel())
-		.pipe(reactPatcher())
-		.on('error', onError)
+		.on('error', function(err) { onError.bind(this)(exitOnError, err); })
 		.on('data', file => {
 			onSuccess(`[js] ${file.path}`);
 		})
+		.pipe(reactPatcher())
 		.pipe(gulp.dest('./build'));
 }
 
-function getJSParallel(source, sourceIgnore) {
+function getJSParallel(source, sourceIgnore, exitOnError = true) {
 	const jsFiles = glob.sync(source, { ignore: sourceIgnore });
 	const cpuCount = os.cpus().length;
 	const threadCount = Math.min(cpuCount, jsFiles.length);
 	let threadsActive = threadCount;
+	let isError = false;
 
 	return new Promise((resolve, reject) => {
 		for(let i = 0; i < threadCount; i++) {
 			let worker = new Worker('gulp/babel-worker.js');
+			workers[i] = worker;
 			worker.onmessage = ev => {
-				if(ev.data.isError) {
-					reject(`Failed while processing ${ev.data.sourcefile}`);
+				if(ev.data.error) {
+					isError = true;
+					let errorMsg = `Failed while processing ${ev.data.sourcefile}: ${ev.data.error}`;
+					NODE_ENV == 'debug' && console.log(`process ${i}: ${errorMsg}`);
+					onError(exitOnError, errorMsg);
+					reject(errorMsg);
 				}
 
 				NODE_ENV == 'debug' && console.log(`process ${i} took ${ev.data.processingTime} ms to process ${ev.data.sourcefile}`);
@@ -132,11 +158,13 @@ function getJSParallel(source, sourceIgnore) {
 				}
 				let nextFile = jsFiles.pop();
 
-				if(nextFile) {
+				if(!isError && nextFile) {
+					NODE_ENV == 'debug' && console.log(`process ${i} scheduled to process ${nextFile}`);
 					worker.postMessage(nextFile);
 				} else {
 					NODE_ENV == 'debug' && console.log(`process ${i} has terminated`);
 					worker.terminate();
+					workers.splice(i, 1);
 					if(!--threadsActive) {
 						resolve();
 					}
@@ -149,7 +177,7 @@ function getJSParallel(source, sourceIgnore) {
 	});
 }
 
-function getSymlinks() {
+function getSymlinks(exitOnError = true) {
 	const match = symlinkFiles
 		.concat(dirs.map(d => `${d}/**`))
 		.concat(symlinkDirs.map(d => `${d}/**`))
@@ -157,27 +185,28 @@ function getSymlinks() {
 		.concat([`!./${formatDirsforMatcher(copyDirs)}/**`]);
 
 	return gulp
-		.src(match, { nodir: true, base: '.', read: false })
-		.on('error', onError)
+		.src(match, { nodir: true, base: '.', read: isWindows })
+		.on('error', function(err) { onError.bind(this)(exitOnError, err); })
 		.on('data', file => {
 			onSuccess(`[ln] ${file.path.substr(__dirname.length + 1)}`);
 		})
-		.pipe(vfs.symlink('build/'));
+		.pipe(isWindows ? gulp.dest('build/') : vfs.symlink('build/'));
 }
 
-function getCopy() {
+function getCopy(exitOnError = true) {
 	return gulp
 		.src(copyDirs.map(d => `${d}/**`), { base: '.' })
 		.on('data', file => {
 			onSuccess(`[cp] ${file.path.substr(__dirname.length + 1)}`);
 		})
+		.on('error', function(err) { onError.bind(this)(exitOnError, err); })
 		.pipe(gulp.dest('build/'));
 }
 
-function getSass() {
+function getSass(exitOnError = true) {
 	return gulp
 		.src('scss/*.scss')
-		.on('error', onError)
+		.on('error', function(err) { onError.bind(this)(exitOnError, err); })
 		.pipe(sass())
 		.pipe(gulp.dest('./build/chrome/skin/default/zotero/components/'));
 }
@@ -192,7 +221,11 @@ gulp.task('symlink', ['clean'], () => {
 });
 
 gulp.task('js', done => {
-	getJSParallel(jsGlob, jsGlobIgnore).then(() => done());
+	getJSParallel(jsGlob, jsGlobIgnore)
+		.then(done)
+		.catch(errorMsg => {
+			onError(errorMsg);
+		});
 });
 
 gulp.task('browserify', () => {
@@ -209,16 +242,21 @@ gulp.task('sass', () => {
 
 gulp.task('build', ['js', 'sass', 'symlink', 'browserify', 'copy']);
 
+gulp.task('build-clean', ['clean'], () => {
+	gulp.start('build');
+});
+
 gulp.task('dev', ['clean'], () => {
 	var interval = 750;
 	
-	let watcher = gulp.watch(jsGlob, { interval });
-
-	watcher.on('change', function(event) {
-		getJS(event.path, jsGlobIgnore);
+	gulp.watch(jsGlob, { interval }).on('change', event => {
+		getJS(event.path, jsGlobIgnore, false);
+	});
+
+	gulp.watch('src/styles/*.scss', { interval }).on('change', () => {
+		getSass(false);
 	});
 
-	gulp.watch('src/styles/*.scss', { interval }, ['sass']);
 	gulp.start('build');
 });
 
diff --git a/package.json b/package.json
index c9a7d82b8..21eeee8b6 100644
--- a/package.json
+++ b/package.json
@@ -6,16 +6,16 @@
   "main": "",
   "scripts": {
     "start": "./node_modules/.bin/gulp",
-    "build": "./node_modules/.bin/gulp",
+    "build": "./node_modules/.bin/gulp build-clean",
     "sass": "./node_modules/.bin/gulp sass",
     "clean": "./node_modules/.bin/gulp clean"
   },
   "license": "",
   "dependencies": {
     "bluebird": "3.4.7",
-    "zotero-web-library": "next",
     "react": "^15.3.2",
-    "react-dom": "^15.3.2"
+    "react-dom": "^15.3.2",
+    "zotero-web-library": "next"
   },
   "devDependencies": {
     "babel-core": "^6.24.1",
@@ -43,6 +43,7 @@
     "gulp-tap": "^1.0.1",
     "gulp-util": "^3.0.7",
     "merge-stream": "^1.0.1",
+    "minimatch": "^3.0.4",
     "mocha": "^3.4.2",
     "sinon": "^2.3.1",
     "through2": "^2.0.1",
diff --git a/test/runtests.sh b/test/runtests.sh
index 945debef6..0a8e24a81 100755
--- a/test/runtests.sh
+++ b/test/runtests.sh
@@ -1,8 +1,8 @@
 #!/bin/bash
 CWD="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-case "$(uname -s)" in
-   CYGWIN*) IS_CYGWIN=1 ;;
+case "$OSTYPE" in
+  msys*|mingw*|cygwin*) IS_CYGWIN=1 ;;
 esac
 
 function makePath {