diff --git a/.gitignore b/.gitignore
index 36bdc4d823..6119e5e5f3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 .idea
+.vscode
 .DS_Store
 npm-debug.log
 
diff --git a/package-lock.json b/package-lock.json
index 568a1537ff..353676949d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -357,7 +357,7 @@
     },
     "@sinonjs/formatio": {
       "version": "2.0.0",
-      "resolved": "https://registry.npmjs.org/@sinonjs/formatio/-/formatio-2.0.0.tgz",
+      "resolved": "http://registry.npmjs.org/@sinonjs/formatio/-/formatio-2.0.0.tgz",
       "integrity": "sha512-ls6CAMA6/5gG+O/IdsBcblvnd8qcO/l1TYoNeAzp3wcISOxlPXQEus0mLcdwazEkWjaBdaJ3TaxmNgCLWwvWzg==",
       "dev": true,
       "requires": {
@@ -1727,7 +1727,7 @@
     },
     "event-stream": {
       "version": "3.3.4",
-      "resolved": "https://registry.npmjs.org/event-stream/-/event-stream-3.3.4.tgz",
+      "resolved": "http://registry.npmjs.org/event-stream/-/event-stream-3.3.4.tgz",
       "integrity": "sha1-SrTJoPWlTbkzi0w02Gv86PSzVXE=",
       "dev": true,
       "requires": {
diff --git a/src/auth/token-generator.ts b/src/auth/token-generator.ts
index c84a32c7f9..fe3dc0c0e3 100644
--- a/src/auth/token-generator.ts
+++ b/src/auth/token-generator.ts
@@ -250,12 +250,7 @@ export class FirebaseTokenGenerator {
     if (typeof developerClaims === 'undefined') {
       return true;
     }
-
-    if (typeof developerClaims === 'object' && developerClaims !== null && !(developerClaims instanceof Array)) {
-      return true;
-    }
-
-    return false;
+    return validator.isNonNullObject(developerClaims);
   }
 
 
diff --git a/src/utils/validator.ts b/src/utils/validator.ts
index ee43110c85..593415e7e6 100644
--- a/src/utils/validator.ts
+++ b/src/utils/validator.ts
@@ -33,7 +33,7 @@ export function isBuffer(value: any): boolean {
  * @return {boolean} Whether the value is an array or not.
  */
 export function isArray(value: any): boolean {
-  return value instanceof Array;
+  return Array.isArray(value);
 }
 
 /**
@@ -98,7 +98,7 @@ export function isNonEmptyString(value: any): boolean {
  * @return {boolean} Whether the value is an object or not.
  */
 export function isObject(value: any): boolean {
-  return typeof value === 'object' && !(value instanceof Array);
+  return typeof value === 'object' && !isArray(value);
 }