diff --git a/addons/website_slides/static/src/slide_category_one2many_field.js b/addons/website_slides/static/src/slide_category_one2many_field.js
index 3fe751b018c..09c990805fd 100644
--- a/addons/website_slides/static/src/slide_category_one2many_field.js
+++ b/addons/website_slides/static/src/slide_category_one2many_field.js
@@ -22,4 +22,5 @@ SlideCategoryOneToManyField.defaultProps = {
 registry.category("fields").add("slide_category_one2many", {
     ...x2ManyField,
     component: SlideCategoryOneToManyField,
+    additionalClasses: [...x2ManyField.additionalClasses || [], "o_field_one2many"],
 });