diff --git a/app/src/js/widgets/fields/fieldRepeater.js b/app/src/js/widgets/fields/fieldRepeater.js
index <HASH>..<HASH> 100644
--- a/app/src/js/widgets/fields/fieldRepeater.js
+++ b/app/src/js/widgets/fields/fieldRepeater.js
@@ -246,10 +246,10 @@
 
             if (this._count >= this.options.maximum) {
                 this._ui.add.addClass('disabled');
-                this.element.find('.duplicate-button').addClass('disabled');
+                this._ui.add.prop('disabled', 'disabled');
             } else {
                 this._ui.add.removeClass('disabled');
-                this.element.find('.duplicate-button').removeClass('disabled');
+                this._ui.add.prop('disabled', false);
             }
 
             if (this._count <= this.options.minimum) {
Fix bug in repeater buttons

Problem:
Currently, when reaching the `limit` in a repeater definition, the [Add
new Repeater set] button gets grayed out but clicking it still adds a
new repeater set, and the [Duplicate set] button also gets wrongly
grayed out.

Fix:
The `.disabled` class was being applied to the [Duplicate set] button,
instead of adding the “disabled” property to the [Add new Repeater set]
button.