diff --git a/package.json b/package.json
index 59011a41..0c17e6e9 100644
--- a/package.json
+++ b/package.json
@@ -35,6 +35,7 @@
   "devDependencies": {
     "babel": "^6.0.15",
     "babel-cli": "^6.1.2",
+    "babel-polyfill": "^6.26.0",
     "babel-preset-env": "^1.6.1",
     "babelify": "^7.3.0",
     "bluebird": "^3.4.6",
@@ -51,6 +52,7 @@
     "mocha": "^4.0.1",
     "node-fetch": "^2.0.0-alpha.9",
     "sinon": "^4.1.3",
-    "sinon-chai": "^2.14.0"
+    "sinon-chai": "^2.14.0",
+    "watchify": "^3.9.0"
   }
 }