configuration.resolve has an unknown property 'fallback'.?

I get this error with my webpack:

Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.

• configuration.resolve has an unknown property 'fallback'. These properties are valid: object { alias?, aliasFields?, cachePredicate?, cacheWithContext?, concord?, descriptionFiles?, enforceExtension?, enforceModuleExtension?, extensions?, fileSystem?, mainFields?, mainFiles?, moduleExtensions?, modules?, plugins?, resolver?, symlinks?, unsafeCache?, useSyncFileSystemCalls? } -> Options for the resolver

My code is:

const webpack = require('webpack'); 
module.exports = function override(config) { 
        const fallback = config.resolve.fallback || {}; 
        Object.assign(fallback, { 
        "crypto": require.resolve("crypto-browserify"), 
      "stream": require.resolve("stream-browserify"), 
      "assert": require.resolve("assert"), 
      "http": require.resolve("stream-http"), 
      "https": require.resolve("https-browserify"), 
      "os": require.resolve("os-browserify"), 
      "url": require.resolve("url") 
      }) 
   config.resolve.fallback = fallback; 
   config.plugins = (config.plugins || []).concat([ 
    new webpack.ProvidePlugin({ 
        process: 'process/browser', 
      Buffer: ['buffer', 'Buffer'] 
    }) 
   ]) 
   return config; }