diff --git a/js/flag-action_link_flash.es6.js b/js/flag-action_link_flash.es6.js
index a0a18f0..ff48c80 100644
--- a/js/flag-action_link_flash.es6.js
+++ b/js/flag-action_link_flash.es6.js
@@ -9,7 +9,7 @@
   // As flag action links are added to the DOM attach a click handler to each
   // link so that styles can be applied while the XHR is in flight.
   Drupal.behaviors.flagAttach = {
-    attach: (context) => {
+    attach (context) {
       const links = context.querySelectorAll('.flag a');
       links.forEach(link => link.addEventListener('click', event => event.target.parentNode.classList.add('flag-waiting')));
     },
diff --git a/js/flag-action_link_flash.js b/js/flag-action_link_flash.js
index 37ee55b..8cb0fe7 100644
--- a/js/flag-action_link_flash.js
+++ b/js/flag-action_link_flash.js
@@ -7,7 +7,7 @@
 
 (function (Drupal) {
   Drupal.behaviors.flagAttach = {
-    attach: context => {
+    attach(context) {
       const links = context.querySelectorAll('.flag a');
       links.forEach(link => link.addEventListener('click', event => event.target.parentNode.classList.add('flag-waiting')));
     }