diff --git a/js/package.json b/js/package.json
index 33668f445..a8cc21e2f 100644
--- a/js/package.json
+++ b/js/package.json
@@ -46,7 +46,7 @@
     "ci:build:npm": "NODE_ENV=production webpack --config webpack/npm",
     "ci:build:jsonrpc": "babel-node ./scripts/build-rpc-json.js --output .npmjs/jsonrpc",
     "ci:build:embed": "NODE_ENV=production EMBED=1 node webpack/embed",
-    "start": "npm install && npm run build:lib && npm run build:dll && npm run start:app",
+    "start": "npm run clean && npm install && npm run build:lib && npm run build:dll && npm run start:app",
     "start:app": "node webpack/dev.server",
     "clean": "rm -rf ./.build ./.coverage ./.happypack ./.npmjs ./build ./node_modules/.cache ./node_modules/@parity",
     "coveralls": "npm run testCoverage && coveralls < coverage/lcov.info",