diff --git a/js/src/dom/polyfill.js b/js/src/dom/polyfill.js
index 2c811c25af..159884df89 100644
--- a/js/src/dom/polyfill.js
+++ b/js/src/dom/polyfill.js
@@ -7,6 +7,7 @@ import Util from '../util'
  * --------------------------------------------------------------------------
  */
 
+/* istanbul ignore next */
 const Polyfill = (() => {
   // defaultPrevented is broken in IE
   const workingDefaultPrevented = (() => {