diff --git a/example/gulp/multi/gulpfile.js b/example/gulp/multi/gulpfile.js
new file mode 100644
index 0000000..24b4184
--- /dev/null
+++ b/example/gulp/multi/gulpfile.js
@@ -0,0 +1,65 @@
+'use strict'
+
+const reduce = require('../../..')
+const gulp = require('gulp')
+const path = require('path')
+const del = require('del')
+
+gulp.task('clean', function () {
+  return del(path.join(__dirname, 'build'))
+})
+
+gulp.task('build', ['clean'], function () {
+  let basedir = path.join(__dirname, 'src')
+  let b = reduce.create({
+    basedir: basedir,
+    paths: [path.join(basedir, 'web_modules')],
+  })
+
+  // As multiple bundles are created,
+  // it is important to deal with duplicates carefully.
+  // There are known issues caused in such cases.
+  // See https://github.com/substack/factor-bundle/issues/51
+  // This plugin will just disable the default dedupe transform.
+  b.plugin('dedupify')
+  b.on('dedupify.deduped', function (o) {
+    console.warn('Duplicates of modules found!', o.file, o.dup)
+  })
+
+  return gulp.src('page/**/index.js', { cwd: basedir })
+    .pipe(reduce.bundle(b, {
+      // This object is passed to `common-bundle`.
+      groups: 'page/**/index.js',
+      common: 'common.js',
+    }))
+    .pipe(gulp.dest('build'))
+})
+
+gulp.task('watch', ['clean'], function () {
+  let clean = require('clean-remains')([])
+  let basedir = path.join(__dirname, 'src')
+  let b = reduce.create({
+    basedir: basedir,
+    paths: [path.join(basedir, 'web_modules')],
+    cache: {},
+    packageCache: {},
+  })
+  b.plugin('dedupify')
+  b.on('dedupify.deduped', function (o) {
+    console.warn('Duplicates of modules found!', o.file, o.dup)
+  })
+  return gulp.src('page/**/index.js', { cwd: basedir })
+    .pipe(reduce.watch(b, {
+      groups: 'page/**/index.js',
+      common: 'common.js',
+    }, { entryGlob: 'page/**/index.js' }))
+    .on('bundle', function (bundleStream) {
+      bundleStream
+        .pipe(gulp.dest('build'))
+        // This plugin will remove files created in the building history but no longer in the newest build.
+        .pipe(clean())
+        .on('data', file => console.log('bundle:', file.relative))
+        .on('end', () => console.log('-'.repeat(40)))
+    })
+})
+
diff --git a/example/gulp/multiple-bundles/src/node_modules/exclamation/excl.js b/example/gulp/multi/src/node_modules/exclamation/excl.js
similarity index 100%
rename from example/gulp/multiple-bundles/src/node_modules/exclamation/excl.js
rename to example/gulp/multi/src/node_modules/exclamation/excl.js
diff --git a/example/gulp/multiple-bundles/src/node_modules/exclamation/package.json b/example/gulp/multi/src/node_modules/exclamation/package.json
similarity index 100%
rename from example/gulp/multiple-bundles/src/node_modules/exclamation/package.json
rename to example/gulp/multi/src/node_modules/exclamation/package.json
diff --git a/example/gulp/multiple-bundles/src/page/hello/index.js b/example/gulp/multi/src/page/hello/index.js
similarity index 100%
rename from example/gulp/multiple-bundles/src/page/hello/index.js
rename to example/gulp/multi/src/page/hello/index.js
diff --git a/example/gulp/multiple-bundles/src/page/hey/index.js b/example/gulp/multi/src/page/hi/index.js
similarity index 100%
rename from example/gulp/multiple-bundles/src/page/hey/index.js
rename to example/gulp/multi/src/page/hi/index.js
diff --git a/example/gulp/multiple-bundles/src/web_modules/lib/world.js b/example/gulp/multi/src/web_modules/lib/world.js
similarity index 100%
rename from example/gulp/multiple-bundles/src/web_modules/lib/world.js
rename to example/gulp/multi/src/web_modules/lib/world.js
diff --git a/example/gulp/multiple-bundles/gulpfile.js b/example/gulp/multiple-bundles/gulpfile.js
deleted file mode 100644
index 04ff345..0000000
--- a/example/gulp/multiple-bundles/gulpfile.js
+++ /dev/null
@@ -1,59 +0,0 @@
-'use strict'
-
-const reduce = require('../../..')
-const gulp = require('gulp')
-const path = require('path')
-const del = require('del')
-
-gulp.task('clean', function () {
-  return del(path.join(__dirname, 'build'))
-})
-
-gulp.task('build', ['clean'], function () {
-  let b = createBundler()
-  return gulp.src('page/**/index.js', { cwd: b._options.basedir })
-    .pipe(reduce.bundle(b, {
-      groups: 'page/**/index.js',
-      common: 'common.js',
-    }))
-    .pipe(gulp.dest('build'))
-})
-
-gulp.task('watch', ['clean'], function (cb) {
-  let b = createBundler()
-  let clean = require('clean-remains')([])
-  b.on('bundle-stream', function (bundleStream) {
-    bundleStream
-      .pipe(gulp.dest('build'))
-      .pipe(clean())
-  })
-  gulp.src('page/**/index.js', { cwd: b._options.basedir })
-    .pipe(reduce.watch(b, {
-      groups: 'page/**/index.js',
-      common: 'common.js',
-    }, { entryGlob: 'page/**/index.js' }))
-})
-
-function createBundler() {
-  let basedir = path.join(__dirname, 'src')
-  let b = reduce.create({
-    basedir: basedir,
-    paths: [path.join(basedir, 'web_modules')],
-    fileCache: {},
-    cache: {},
-    packageCache: {},
-  })
-
-  b.plugin('dedupify')
-  b.on('dedupify.deduped', function (o) {
-    console.warn('Duplicates of modules found!', o.file, o.dup)
-  })
-
-  b.on('error', console.log.bind(console))
-  b.on('common.map', function (map) {
-    console.log('bundles:', '[ ' + Object.keys(map).join(', ') + ' ]')
-  })
-
-  return b
-}
-
diff --git a/example/gulp/single-bundle/gulpfile.js b/example/gulp/reduce/gulpfile.js
similarity index 55%
rename from example/gulp/single-bundle/gulpfile.js
rename to example/gulp/reduce/gulpfile.js
index 6371f44..f594972 100644
--- a/example/gulp/single-bundle/gulpfile.js
+++ b/example/gulp/reduce/gulpfile.js
@@ -10,37 +10,33 @@ gulp.task('clean', function () {
 })
 
 gulp.task('build', ['clean'], function () {
-  let b = createBundler()
-  return gulp.src('page/**/index.js', { cwd: b._options.basedir })
+  let basedir = path.join(__dirname, 'src')
+  let b = reduce.create({
+    basedir: basedir,
+    paths: [path.join(basedir, 'web_modules')],
+  })
+  return gulp.src('page/**/index.js', { cwd: basedir })
     .pipe(reduce.bundle(b, 'bundle.js'))
     .pipe(gulp.dest('build'))
 })
 
-gulp.task('watch', ['clean'], function (cb) {
-  let b = createBundler()
-  b.plugin(require('clean-remains')([]))
-  b.on('bundle-stream', function (bundleStream) {
-    bundleStream.pipe(gulp.dest('build'))
-  })
-  gulp.src('page/**/index.js', { cwd: b._options.basedir })
-    .pipe(reduce.watch(b, 'bundle.js', { entryGlob: 'page/**/index.js' }))
-})
-
-function createBundler() {
+gulp.task('watch', ['clean'], function () {
+  let clean = require('clean-remains')([])
   let basedir = path.join(__dirname, 'src')
   let b = reduce.create({
     basedir: basedir,
     paths: [path.join(basedir, 'web_modules')],
-    fileCache: {},
     cache: {},
     packageCache: {},
   })
-
-  b.on('error', console.log.bind(console))
-  b.on('common.map', function (map) {
-    console.log('bundles:', '[ ' + Object.keys(map).join(', ') + ' ]')
-  })
-
-  return b
-}
+  return gulp.src('page/**/index.js', { cwd: b._options.basedir })
+    .pipe(reduce.watch(b, 'bundle.js', { entryGlob: 'page/**/index.js' }))
+    .on('bundle', function (bundleStream) {
+      bundleStream
+        .pipe(gulp.dest('build'))
+        .pipe(clean())
+        .on('data', file => console.log('bundle:', file.relative))
+        .on('end', () => console.log('-'.repeat(40)))
+    })
+})
 
diff --git a/example/gulp/single-bundle/src/node_modules/exclamation/excl.js b/example/gulp/reduce/src/node_modules/exclamation/excl.js
similarity index 100%
rename from example/gulp/single-bundle/src/node_modules/exclamation/excl.js
rename to example/gulp/reduce/src/node_modules/exclamation/excl.js
diff --git a/example/gulp/single-bundle/src/node_modules/exclamation/package.json b/example/gulp/reduce/src/node_modules/exclamation/package.json
similarity index 100%
rename from example/gulp/single-bundle/src/node_modules/exclamation/package.json
rename to example/gulp/reduce/src/node_modules/exclamation/package.json
diff --git a/example/gulp/single-bundle/src/page/hello/index.js b/example/gulp/reduce/src/page/hello/index.js
similarity index 100%
rename from example/gulp/single-bundle/src/page/hello/index.js
rename to example/gulp/reduce/src/page/hello/index.js
diff --git a/example/gulp/multiple-bundles/src/page/hi/index.js b/example/gulp/reduce/src/page/hi/index.js
similarity index 100%
rename from example/gulp/multiple-bundles/src/page/hi/index.js
rename to example/gulp/reduce/src/page/hi/index.js
diff --git a/example/gulp/single-bundle/src/web_modules/lib/world.js b/example/gulp/reduce/src/web_modules/lib/world.js
similarity index 100%
rename from example/gulp/single-bundle/src/web_modules/lib/world.js
rename to example/gulp/reduce/src/web_modules/lib/world.js
diff --git a/example/gulp/single-bundle/src/page/hi/index.js b/example/gulp/single-bundle/src/page/hi/index.js
deleted file mode 100644
index 1eeefb8..0000000
--- a/example/gulp/single-bundle/src/page/hi/index.js
+++ /dev/null
@@ -1,3 +0,0 @@
-var world = require('lib/world')
-module.exports = 'hi, ' + world
-
diff --git a/example/node_modules/reduce-js b/example/node_modules/reduce-js
new file mode 120000
index 0000000..5207c3e
--- /dev/null
+++ b/example/node_modules/reduce-js
@@ -0,0 +1 @@
+../../../reduce-js
\ No newline at end of file
diff --git a/example/without-gulp/build.js b/example/without-gulp/build.js
index ac71b17..6eb8a92 100644
--- a/example/without-gulp/build.js
+++ b/example/without-gulp/build.js
@@ -1,18 +1,18 @@
 'use strict'
 
-const reduce = require('../..')
+const reduce = require('reduce-js')
 const del = require('del')
 
 const basedir = __dirname + '/src'
 const build = __dirname + '/build'
 del(build).then(function () {
   let b = reduce.create({ basedir: basedir })
-
   b.on('error', err => console.log(err))
-  b.on('common.map', map => console.log(map))
 
   reduce.src('*.js', { cwd: basedir })
     .pipe(reduce.bundle(b, 'bundle.js'))
     .pipe(reduce.dest(build))
+    .on('data', file => console.log('bundle:', file.relative))
+    .on('end', () => console.log('DONE'))
 })
 
diff --git a/example/without-gulp/default-watch.js b/example/without-gulp/default-watch.js
index cdd8299..cc746dd 100644
--- a/example/without-gulp/default-watch.js
+++ b/example/without-gulp/default-watch.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const reduce = require('../..')
+const reduce = require('reduce-js')
 const del = require('del')
 
 const basedir = __dirname + '/src'
diff --git a/example/without-gulp/default.js b/example/without-gulp/default.js
index f636278..4e8560b 100644
--- a/example/without-gulp/default.js
+++ b/example/without-gulp/default.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const reduce = require('../..')
+const reduce = require('reduce-js')
 const del = require('del')
 
 const basedir = __dirname + '/src'
diff --git a/example/without-gulp/stream-input.js b/example/without-gulp/stream-input.js
index 8c11d65..54a627d 100644
--- a/example/without-gulp/stream-input.js
+++ b/example/without-gulp/stream-input.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const reduce = require('../..')
+const reduce = require('reduce-js')
 const del = require('del')
 const fs = require('fs')
 const source = require('vinyl-source-stream')
diff --git a/example/without-gulp/watch.js b/example/without-gulp/watch.js
index abfda21..a513d43 100644
--- a/example/without-gulp/watch.js
+++ b/example/without-gulp/watch.js
@@ -1,7 +1,6 @@
 'use strict'
 
-const reduce = require('../..')
-const path = require('path')
+const reduce = require('reduce-js')
 const del = require('del')
 
 const basedir = __dirname + '/src'
@@ -13,14 +12,14 @@ del(build).then(function () {
     packageCache: {},
     fileCache: {},
   })
+  b.on('error', err => console.log(err.stack))
 
-  b.on('error', err => console.log(err))
-  b.on('common.map', map => console.log(map))
-
-  b.on('bundle-stream', function (bundleStream) {
-    bundleStream.pipe(reduce.dest(build))
-  })
   reduce.src('*.js', { cwd: basedir })
     .pipe(reduce.watch(b, 'bundle.js', { entryGlob: '*.js' }))
+    .on('bundle', function (bundleStream) {
+      bundleStream.pipe(reduce.dest(build))
+      .on('data', file => console.log('bundle:', file.relative))
+      .on('end', () => console.log('-'.repeat(40)))
+    })
 })
 
diff --git a/index.js b/index.js
index 040f854..e64181e 100644
--- a/index.js
+++ b/index.js
@@ -102,6 +102,7 @@ function watch(b, opts, wopts) {
       next()
     },
     function (next) {
+      b.on('bundle-stream', s => this.emit('bundle', s))
       b.once('close', next)
       b.start()
     }