diff --git a/lib/helpers/isURLSameOrigin.js b/lib/helpers/isURLSameOrigin.js
index a8678a4..5a91e89 100644
--- a/lib/helpers/isURLSameOrigin.js
+++ b/lib/helpers/isURLSameOrigin.js
@@ -8,7 +8,7 @@ export default platform.hasStandardBrowserEnv ?
 // Standard browser envs have full support of the APIs needed to test
 // whether the request URL is of the same origin as current location.
   (function standardBrowserEnv() {
-    const msie = /(msie|trident)/i.test(navigator.userAgent);
+    const msie = platform.navigator && /(msie|trident)/i.test(platform.navigator.userAgent);
     const urlParsingNode = document.createElement('a');
     let originURL;
 
diff --git a/lib/platform/common/utils.js b/lib/platform/common/utils.js
index d60921b..52a3186 100644
--- a/lib/platform/common/utils.js
+++ b/lib/platform/common/utils.js
@@ -1,5 +1,7 @@
 const hasBrowserEnv = typeof window !== 'undefined' && typeof document !== 'undefined';
 
+const _navigator = typeof navigator === 'object' && navigator || undefined;
+
 /**
  * Determine if we're running in a standard browser environment
  *
@@ -17,10 +19,8 @@ const hasBrowserEnv = typeof window !== 'undefined' && typeof document !== 'unde
  *
  * @returns {boolean}
  */
-const hasStandardBrowserEnv = (
-  (product) => {
-    return hasBrowserEnv && ['ReactNative', 'NativeScript', 'NS'].indexOf(product) < 0
-  })(typeof navigator !== 'undefined' && navigator.product);
+const hasStandardBrowserEnv = hasBrowserEnv &&
+  (!_navigator || ['ReactNative', 'NativeScript', 'NS'].indexOf(_navigator.product) < 0);
 
 /**
  * Determine if we're running in a standard browser webWorker environment
@@ -46,5 +46,6 @@ export {
   hasBrowserEnv,
   hasStandardBrowserWebWorkerEnv,
   hasStandardBrowserEnv,
+  _navigator as navigator,
   origin
 }