diff --git a/js/builder.js b/js/builder.js
index 1e8840d9bc0d0a1e4742d65ed7ea84cd19be921b..2fb54e0795f299cbb7e9c54ea1ed591544a5be37 100644
--- a/js/builder.js
+++ b/js/builder.js
@@ -417,17 +417,15 @@
    * API for adding Layout Paragraphs Sortable.js instances.
    */
   Drupal.LPSortableInstances = {
-    intances: {},
+    instances: new Map(),
     add: function (id, instance) {
-      if (this.intances[id]) {
-        this.intances[id].push(instance);
-      }
-      else {
-        this.intances[id] = [instance];
+      if (!this.instances.has(id)) {
+        this.instances.set(id, new Set());
       }
+      this.instances.get(id).add(instance);
     },
     get: function (id) {
-      return this.intances[id] || [];
+      return this.instances.get(id) || new Set();
     }
   };