diff --git a/js/schedule.js b/js/schedule.js
index 4a6604655..5f260b26f 100644
--- a/js/schedule.js
+++ b/js/schedule.js
@@ -1,3 +1,5 @@
+import "core-js/stable/object/group-by";
+
 import React from 'react';
 import ReactDOM from 'react-dom';