diff --git a/packages/node_modules/@node-red/editor-client/src/js/ui/editors/json.js b/packages/node_modules/@node-red/editor-client/src/js/ui/editors/json.js
index 3b83e3089..67b5850c4 100644
--- a/packages/node_modules/@node-red/editor-client/src/js/ui/editors/json.js
+++ b/packages/node_modules/@node-red/editor-client/src/js/ui/editors/json.js
@@ -106,7 +106,7 @@
             options.push({id:"red-ui-editor-type-json-menu-duplicate", icon:"fa fa-copy", label:RED._("jsonEditor.duplicate"),onselect:function(){
                 var newKey = item.key;
                 if (item.parent.type === 'array') {
-                    newKey = parent.children.length;
+                    newKey = item.parent.children.length;
                 } else {
                     var m = /^(.*?)(-(\d+))?$/.exec(newKey);
                     var usedKeys = {};