diff --git a/src/auth/credential.ts b/src/auth/credential.ts
index b526c338c1..38d7945812 100644
--- a/src/auth/credential.ts
+++ b/src/auth/credential.ts
@@ -14,15 +14,10 @@
  * limitations under the License.
  */
 
-import * as jwt from 'jsonwebtoken';
-import * as forge from 'node-forge';
-
 // Use untyped import syntax for Node built-ins
 import fs = require('fs');
 import os = require('os');
-import http = require('http');
 import path = require('path');
-import https = require('https');
 
 import {AppErrorCodes, FirebaseAppError} from '../utils/error';
 
@@ -169,6 +164,7 @@ export class Certificate {
       throw new FirebaseAppError(AppErrorCodes.INVALID_CREDENTIAL, errorMessage);
     }
 
+    const forge = require('node-forge');
     try {
       forge.pki.privateKeyFromPem(this.privateKey);
     } catch (error) {
@@ -257,6 +253,7 @@ export class CertCredential implements Credential {
         'Content-Length': postData.length,
       },
     };
+    const https = require('https');
     return requestAccessToken(https, options, postData);
   }
 
@@ -275,6 +272,7 @@ export class CertCredential implements Credential {
       ].join(' '),
     };
 
+    const jwt = require('jsonwebtoken');
     // This method is actually synchronous so we can capture and return the buffer.
     return jwt.sign(claims, this.certificate_.privateKey, {
       audience: GOOGLE_TOKEN_AUDIENCE,
@@ -321,6 +319,7 @@ export class RefreshTokenCredential implements Credential {
         'Content-Length': postData.length,
       },
     };
+    const https = require('https');
     return requestAccessToken(https, options, postData);
   }
 
@@ -345,6 +344,7 @@ export class MetadataServiceCredential implements Credential {
         'Content-Length': 0,
       },
     };
+    const http = require('http');
     return requestAccessToken(http, options);
   }
 
diff --git a/src/firebase-app.ts b/src/firebase-app.ts
index 75c083c9a6..be0b2da6ac 100644
--- a/src/firebase-app.ts
+++ b/src/firebase-app.ts
@@ -286,7 +286,8 @@ export class FirebaseApp {
    */
   public auth(): Auth {
     return this.ensureService_('auth', () => {
-      return new Auth(this);
+      const authService: typeof Auth = require('./auth/auth').Auth;
+      return new authService(this);
     });
   }
 
@@ -297,7 +298,8 @@ export class FirebaseApp {
    */
   public database(url?: string): Database {
     const service: DatabaseService = this.ensureService_('database', () => {
-      return new DatabaseService(this);
+      const dbService: typeof DatabaseService = require('./database/database').DatabaseService;
+      return new dbService(this);
     });
     return service.getDatabase(url);
   }
@@ -309,7 +311,8 @@ export class FirebaseApp {
    */
   public messaging(): Messaging {
     return this.ensureService_('messaging', () => {
-      return new Messaging(this);
+      const messagingService: typeof Messaging = require('./messaging/messaging').Messaging;
+      return new messagingService(this);
     });
   }
 
@@ -320,13 +323,15 @@ export class FirebaseApp {
    */
   public storage(): Storage {
     return this.ensureService_('storage', () => {
-      return new Storage(this);
+      const storageService: typeof Storage = require('./storage/storage').Storage;
+      return new storageService(this);
     });
   }
 
   public firestore(): Firestore {
     const service: FirestoreService = this.ensureService_('firestore', () => {
-      return new FirestoreService(this);
+      const firestoreService: typeof FirestoreService = require('./firestore/firestore').FirestoreService;
+      return new firestoreService(this);
     });
     return service.client;
   }
@@ -338,7 +343,8 @@ export class FirebaseApp {
    */
   public instanceId(): InstanceId {
     return this.ensureService_('iid', () => {
-      return new InstanceId(this);
+      const iidService: typeof InstanceId = require('./instance-id/instance-id').InstanceId;
+      return new iidService(this);
     });
   }
 
diff --git a/src/firebase-namespace.ts b/src/firebase-namespace.ts
index 7330a64a66..dcfab00538 100644
--- a/src/firebase-namespace.ts
+++ b/src/firebase-namespace.ts
@@ -325,7 +325,8 @@ export class FirebaseNamespace {
     const fn: FirebaseServiceNamespace<Auth> = (app?: FirebaseApp) => {
       return this.ensureApp(app).auth();
     };
-    return Object.assign(fn, {Auth});
+    const auth = require('./auth/auth').Auth;
+    return Object.assign(fn, {Auth: auth});
   }
 
   /**
@@ -347,7 +348,8 @@ export class FirebaseNamespace {
     const fn: FirebaseServiceNamespace<Messaging> = (app?: FirebaseApp) => {
       return this.ensureApp(app).messaging();
     };
-    return Object.assign(fn, {Messaging});
+    const messaging = require('./messaging/messaging').Messaging;
+    return Object.assign(fn, {Messaging: messaging});
   }
 
   /**
@@ -358,7 +360,8 @@ export class FirebaseNamespace {
     const fn: FirebaseServiceNamespace<Storage> = (app?: FirebaseApp) => {
       return this.ensureApp(app).storage();
     };
-    return Object.assign(fn, {Storage});
+    const storage = require('./storage/storage').Storage;
+    return Object.assign(fn, {Storage: storage});
   }
 
   /**
@@ -380,7 +383,8 @@ export class FirebaseNamespace {
     const fn: FirebaseServiceNamespace<InstanceId> = (app?: FirebaseApp) => {
       return this.ensureApp(app).instanceId();
     };
-    return Object.assign(fn, {InstanceId});
+    const instanceId = require('./instance-id/instance-id').InstanceId;
+    return Object.assign(fn, {InstanceId: instanceId});
   }
 
   /**