DeprecationWarning in webpack v4

[CodeLittlePrince]

description

when I use webpack v4 in this way:

const serverCompiler = webpack(serverConfig)
const MFS = require('memory-fs')
const mfs = new MFS()
serverCompiler.outputFileSystem = mfs

and show the warning below:
DeprecationWarning: Tapable.plugin is deprecated. Use new API on .hooks instead

[ghost]

I had the same problem

[ghost]

This error does not affect the use.