diff --git a/invert-tree/test.js b/invert-tree/test.js
index 8865fc1..fbcd956 100644
--- a/invert-tree/test.js
+++ b/invert-tree/test.js
@@ -51,6 +51,8 @@ describe('invert-tree', function() {
 
     invertTree(root);
 
+    root = JSON.parse(JSON.stringify(root));
+
     assert.deepEqual(root, {
       "value": 4,
       "left": {
@@ -71,6 +73,8 @@ describe('invert-tree', function() {
 
     invertTree(root);
 
+    root = JSON.parse(JSON.stringify(root));
+
     assert.deepEqual(root, {
       "value": 5,
       "right": {