add : HashedModuleIdsPlugin

build/webpack.prod.conf.js

       // necessary to consistently work with multiple chunks via CommonsChunkPlugin
       chunksSortMode: 'dependency'
     }),
+    // cache Module Identifiers
+    new webpack.HashedModuleIdsPlugin(),
     // split vendor js into its own file
     new webpack.optimize.CommonsChunkPlugin({
       name: 'vendor',