diff --git a/src/core/structure/tree.js b/src/core/structure/tree.js
index 32e7665b4..839b51bec 100644
--- a/src/core/structure/tree.js
+++ b/src/core/structure/tree.js
@@ -127,7 +127,9 @@
                     continue;
                 }
                 if (temp != null) {
-                    queue = queue.concat(temp.getChildren());
+                    BI.each(temp.getChildren(), function(_i, t) {
+                        queue.push(t);
+                    })
                 }
             }
         },