diff --git a/app/assets/javascripts/discourse/app/widgets/default-notification-item.js b/app/assets/javascripts/discourse/app/widgets/default-notification-item.js
index ff9d09f2975..d9ab91e2ff0 100644
--- a/app/assets/javascripts/discourse/app/widgets/default-notification-item.js
+++ b/app/assets/javascripts/discourse/app/widgets/default-notification-item.js
@@ -33,7 +33,7 @@ export const DefaultNotificationItem = createWidget(
       const lookup = this.site.get("notificationLookup");
       const notificationName = lookup[notificationType];
       if (notificationName) {
-        classNames.push(notificationName.replaceAll("_", "-"));
+        classNames.push(notificationName.replace(/_/g, "-"));
       }
       return classNames;
     },