diff --git a/packages/react-storybook/src/server/config/defaults/webpack.config.js b/packages/react-storybook/src/server/config/defaults/webpack.config.js
index 69ec7d68f6ab..b82ed7b4864f 100644
--- a/packages/react-storybook/src/server/config/defaults/webpack.config.js
+++ b/packages/react-storybook/src/server/config/defaults/webpack.config.js
@@ -1,5 +1,6 @@
+import webpack from 'webpack';
 import autoprefixer from 'autoprefixer';
-import { includePaths } from '../utils';
+import { includePaths, excludePaths } from '../utils';
 
 // Add a default custom config which is similar to what React Create App does.
 module.exports = storybookBaseConfig => {
@@ -57,12 +58,6 @@ module.exports = storybookBaseConfig => {
     },
   ];
 
-  newConfig.postcss = () => [
-    autoprefixer({
-      browsers: ['>1%', 'last 4 versions', 'Firefox ESR', 'not ie < 9'],
-    }),
-  ];
-
   newConfig.resolve.alias = {
     ...storybookBaseConfig.resolve.alias,
     // This is to support NPM2