diff --git a/lib/client/store.js b/lib/client/store.js
index 68b4535..1ccdacd 100644
--- a/lib/client/store.js
+++ b/lib/client/store.js
@@ -51,7 +51,7 @@ Store.prototype.stop = function() {
 };
 
 Store.prototype.now = function() {
-  if (isPerformanceExists) {
+  if (isPerformanceExists && performance.now) {
     return performance.now();
   }