diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 967975d5b..bfcb59091 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -19,6 +19,14 @@
     <script src="../../blocks/procedures.js"></script>
     <script src="../../blocks/text.js"></script>
   </head>
+  <style>
+    #blocklyDiv {
+      height: 1000px;
+      position: fixed;
+      visibility: hidden;
+      width: 1000px;
+    }
+  </style>
   <body>
 
     <div id="mocha"></div>
