diff --git a/README.md b/README.md
index 120629c..f4da655 100644
--- a/README.md
+++ b/README.md
@@ -70,6 +70,9 @@ return gulp.src('./src/*.css')
 
 ## Changelog
 
+* 5.0.0
+  * Use async API
+
 * 4.0.3
   * Fixed bug with relative source map
 
diff --git a/index.js b/index.js
index 39e7819..02fb8b7 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,4 @@
-var through = require('through2')
+var Stream = require('stream')
 var postcss = require('postcss')
 var applySourceMap = require('vinyl-sourcemaps-apply')
 var gutil = require('gulp-util')
@@ -10,20 +10,17 @@ module.exports = function (processors, options) {
     throw new gutil.PluginError('gulp-postcss', 'Please provide array of postcss processors!')
   }
 
-  return through.obj(transform)
+  var stream = new Stream.Transform({ objectMode: true })
 
-  function transform (file, encoding, cb) {
+  stream._transform = function (file, encoding, cb) {
 
     if (file.isStream()) {
-      return cb(new gutil.PluginError('gulp-postcss', 'Streams are not supported!'))
+      return handleError('Streams are not supported!')
     }
 
     // Source map is disabled by default
     var opts = { map: false }
-    var processor = postcss()
-    var result
     var attr
-    var map
 
     // Extend default options
     if (options) {
@@ -42,25 +39,36 @@ module.exports = function (processors, options) {
     }
 
     try {
-      processors.forEach(processor.use.bind(processor))
-      result = processor.process(file.contents.toString('utf8'), opts)
-    } catch (err) {
-      return cb(new gutil.PluginError('gulp-postcss', err))
+      postcss(processors)
+        .process(file.contents, opts)
+        .then(handleResult, handleError)
+    } catch (error) {
+      handleError(error)
     }
 
-    file.contents = new Buffer(result.css)
+    function handleResult (result) {
+      var map
 
-    // Apply source map to the chain
-    if (file.sourceMap) {
-      map = result.map.toJSON()
-      map.file = file.relative
-      map.sources = [].map.call(map.sources, function (source) {
-        return path.relative(file.base, source)
-      })
-      applySourceMap(file, map)
+      file.contents = new Buffer(result.css)
+
+      // Apply source map to the chain
+      if (file.sourceMap) {
+        map = result.map.toJSON()
+        map.file = file.relative
+        map.sources = [].map.call(map.sources, function (source) {
+          return path.relative(file.base, source)
+        })
+        applySourceMap(file, map)
+      }
+
+      cb(null, file)
+    }
+
+    function handleError (error) {
+      cb(new gutil.PluginError('gulp-postcss', error))
     }
 
-    cb(null, file)
   }
 
+  return stream
 }
diff --git a/package.json b/package.json
index de9a641..26e1854 100644
--- a/package.json
+++ b/package.json
@@ -1,10 +1,10 @@
 {
   "name": "gulp-postcss",
-  "version": "4.0.3",
+  "version": "5.0.0",
   "description": "PostCSS gulp plugin",
   "main": "index.js",
   "scripts": {
-    "test": "mocha"
+    "test": "mocha test.js"
   },
   "repository": {
     "type": "git",
@@ -22,13 +22,13 @@
   },
   "homepage": "https://github.com/w0rm/gulp-postcss",
   "dependencies": {
-    "gulp-util": "^3.0.0",
-    "postcss": "^4.0.1",
-    "through2": "^0.6.1",
-    "vinyl-sourcemaps-apply": "^0.1.1"
+    "gulp-util": "^3.0.4",
+    "postcss": "^4.1.0",
+    "vinyl-sourcemaps-apply": "^0.1.4"
   },
   "devDependencies": {
-    "gulp-sourcemaps": "^1.1.5",
-    "mocha": "^1.21.4"
+    "gulp-sourcemaps": "^1.5.1",
+    "mocha": "^2.2.1",
+    "promise": "^6.1.0"
   }
 }
diff --git a/test.js b/test.js
index ffa225e..7cbe2a6 100644
--- a/test.js
+++ b/test.js
@@ -4,11 +4,12 @@ var assert = require('assert')
 var gutil = require('gulp-util')
 var sourceMaps = require('gulp-sourcemaps')
 var postcss = require('./index')
+var Promise = require('promise')
 
 it('should transform css with multiple processors', function (cb) {
 
   var stream = postcss(
-    [ doubler, doubler ]
+    [ asyncDoubler, doubler ]
   )
 
   stream.on('data', function (file) {
@@ -46,7 +47,7 @@ it('should correctly wrap postcss errors', function (cb) {
 })
 
 
-it ('should throw error if processors are not provided', function (cb) {
+it('should throw error if processors are not provided', function (cb) {
   assert.throws( function () { postcss() }, gutil.PluginError )
   assert.throws( function () { postcss('') }, gutil.PluginError )
   assert.throws( function () { postcss({}) }, gutil.PluginError )
@@ -54,12 +55,12 @@ it ('should throw error if processors are not provided', function (cb) {
 })
 
 
-it ('should generate source maps', function (cb) {
+it('should generate source maps', function (cb) {
 
   var init = sourceMaps.init()
   var write = sourceMaps.write()
   var css = postcss(
-    [ doubler, doubler ]
+    [ doubler, asyncDoubler ]
   )
 
   init
@@ -67,7 +68,7 @@ it ('should generate source maps', function (cb) {
     .pipe(write)
 
   write.on('data', function (file) {
-    assert.equal(file.sourceMap.mappings, 'AAAA,IAAI,cAAA,AAAY,cAAZ,AAAY,cAAZ,AAAY,aAAA,EAAE')
+    assert.equal(file.sourceMap.mappings, 'AAAA,IAAI,aAAY,CAAZ,aAAY,CAAZ,aAAY,CAAZ,YAAY,EAAE')
     assert(/sourceMappingURL=data:application\/json;base64/.test(file.contents.toString()))
     cb()
   })
@@ -83,7 +84,7 @@ it ('should generate source maps', function (cb) {
 })
 
 
-it ('should correctly generate relative source map', function (cb) {
+it('should correctly generate relative source map', function (cb) {
 
   var init = sourceMaps.init()
   var css = postcss(
@@ -114,3 +115,12 @@ function doubler (css) {
     decl.parent.prepend(decl.clone())
   })
 }
+
+function asyncDoubler (css) {
+  return new Promise(function (resolve) {
+    setTimeout(function () {
+      doubler(css)
+      resolve()
+    })
+  })
+}