diff --git a/docs/example/tests.html b/docs/example/tests.html
index 77e99ddf2a..24c1f8d67d 100644
--- a/docs/example/tests.html
+++ b/docs/example/tests.html
@@ -9,7 +9,7 @@
   <body>
     <div id="mocha"></div>
     <script src="https://unpkg.com/mocha/mocha.js"></script>
-    <script src="https://unpkg.com/chai/chai.js"></script>
+    <script src="https://unpkg.com/chai@4.5.0/chai.js"></script>
     <script>mocha.setup('bdd')</script>
     <script>expect = chai.expect</script>
     <script src="Array.js"></script>
