ecmascript 6 - Webpack build failed when a file imported some files which are not under current working directory -

app
  +---commonmodule
  |    +---reducers
  |    |      +--- gradereducer.js
  +---myapp
  |    +---reducers
  |    |      +---reducers.js
  |    +---components
  |    +---actions
  |    +---containers
  |    +---webpack.config.js

based on above structure, tried import gradereducer.js in reducers.js. webpack can't build it. says

"referenceerror: unknown plugin "transform-runtime" specified in "base" @ 0"

if put gradereducer.js under myapp/reducers directory, webpack can build successfully.