diff --git a/src/core/structure/tree.js b/src/core/structure/tree.js
index 32e7665b4..d79ac99ef 100644
--- a/src/core/structure/tree.js
+++ b/src/core/structure/tree.js
@@ -127,7 +127,7 @@
                     continue;
                 }
                 if (temp != null) {
-                    queue = queue.concat(temp.getChildren());
+                    queue.push(...temp.getChildren());
                 }
             }
         },