diff --git a/packages/opencensus-web-core/package.json b/packages/opencensus-web-core/package.json
index 41fe3ace..6a98a4af 100644
--- a/packages/opencensus-web-core/package.json
+++ b/packages/opencensus-web-core/package.json
@@ -59,7 +59,8 @@
     "ts-loader": "^6.0.0",
     "typescript": "^3.1.6",
     "webpack": "^4.18.0",
-    "webpack-cli": "^3.1.0"
+    "webpack-cli": "^3.1.0",
+    "zone.js": "^0.9.1"
   },
   "dependencies": {
     "@opencensus/web-types": "^0.0.3"