webpack-dev-server: v2.6.1 CachedInputFileSystem error

if watch is enabled in webpack config:

/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:145
			if(key.startsWith(what))
			      ^

TypeError: Cannot read property 'startsWith' of undefined
    at Storage.purge (/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:145:10)
    at Storage.purge (/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:150:9)
    at CachedInputFileSystem.purge (/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:259:20)
    at EventEmitter.watcher.once (/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/webpack/lib/node/NodeWatchFileSystem.js:42:26)
    at EventEmitter.g (events.js:291:16)
    at emitTwo (events.js:106:13)
    at EventEmitter.emit (events.js:191:7)
    at EventEmitter._onTimeout (/Users/burak.demirezen/Documents/Projects/widget-v3-configurator/node_modules/watchpack/lib/watchpack.js:142:7)
    at ontimeout (timers.js:365:14)
    at tryOnTimeout (timers.js:237:5)
    at Timer.listOnTimeout (timers.js:207:5)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! broadage-widget-v3-configurator@1.0.0 deploy-dev: `webpack --config webpack-dev.config.js --colors --progress --profile`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the broadage-widget-v3-configurator@1.0.0 deploy-dev script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/burak.demirezen/.npm/_logs/2017-07-24T08_53_53_623Z-debug.log