diff --git a/lib/filter.js b/lib/filter.js
index 5758700..1993a21 100644
--- a/lib/filter.js
+++ b/lib/filter.js
@@ -45,8 +45,8 @@ function logicCss (str, data) {
     if (nanomatch.some(path, exclude, { matchBase: true })) return str
   }
 
-  return new Promise(function (resolve, reject) {
-    new CleanCSS(options).minify(str, function (err, result) {
+  return new Promise((resolve, reject) => {
+    new CleanCSS(options).minify(str, (err, result) => {
       if (err) return reject(err)
       let saved = ((str.length - result.styles.length) / str.length * 100).toFixed(2)
       resolve(result.styles)
@@ -107,7 +107,7 @@ function logicSvg () {
       assetPath.on('end', () => {
         if (assetTxt.length) {
           // Minify using svgo
-          new svgo(options).optimize(assetTxt).then(function (result) {
+          new svgo(options).optimize(assetTxt).then((result) => {
             // Replace the original file with the minified.
             route.set(path, result.data)
             // Logging