Webpack – extract-text-webpack-plugin无法find模块

webpack.config.js

var ExtractTextPlugin = require("extract-text-webpack-plugin"); 

我马上收到这个错误,如果我只是实现插件:

 module.js:339 throw err; ^ Error: Cannot find module 'webpack/lib/ConcatSource' at Function.Module._resolveFilename (module.js:337:15) at Function.Module._load (module.js:287:25) at Module.require (module.js:366:17) at require (module.js:385:17) at Object.<anonymous> (/Users/lucamormile/Documents/Lavori/Webapps/React/webpack_test/node_modules/extract-text-webpack-plugin/index.js:5:20) at Module._compile (module.js:425:26) at Object.Module._extensions..js (module.js:432:10) at Module.load (module.js:356:32) at Function.Module._load (module.js:311:12) at Module.require (module.js:366:17) 

我忘了什么

       

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