Firebase admin SDK in ionic2: Cannot find module "dns"

I'm trying to use Firebase admin SDK as explained here in ionic2. but when I call admin.initializeApp, I get this error:

  import * as admin from "firebase-admin";
  ....
  admin.initializeApp({
  credential: admin.credential.cert({
    projectId: "<PROJECT_ID>",
    clientEmail: "foo@<PROJECT_ID>.iam.gserviceaccount.com",
    privateKey: "-----BEGIN PRIVATE KEY-----\n<KEY>\n-----END PRIVATE KEY-----\n"
  }),
  databaseURL: "https://<DATABASE_NAME>.firebaseio.com"
});


Error: Cannot find module "dns"
at webpackMissingModule (http://localhost:8101/build/main.js:178777:75)
at Object.<anonymous> (http://localhost:8101/build/main.js:178777:156)
at Object.<anonymous> (http://localhost:8101/build/main.js:180128:30)
at __webpack_require__ (http://localhost:8101/build/main.js:20:30)
at Object.<anonymous> (http://localhost:8101/build/main.js:178726:18)
at __webpack_require__ (http://localhost:8101/build/main.js:20:30)
at Object.<anonymous> (http://localhost:8101/build/main.js:132218:15)
at Object.internals.rfc3986 (http://localhost:8101/build/main.js:132683:30)
at __webpack_require__ (http://localhost:8101/build/main.js:20:30)
at Object.<anonymous> (http://localhost:8101/build/main.js:42488:13)

I have installed dns module by npm install dns, but still get this error. Any ideas how I can fix this?

via Ari