diff --git a/src/arrayToTree.ts b/src/arrayToTree.ts
index 4271cfc..380075b 100644
--- a/src/arrayToTree.ts
+++ b/src/arrayToTree.ts
@@ -85,10 +85,9 @@ export function arrayToTree(
     if (conf.dataField) {
       lookup[itemId][conf.dataField] = item;
     } else {
-      lookup[itemId] = {
-        ...item,
-        [conf.childrenField]: lookup[itemId][conf.childrenField],
-      };
+      lookup[itemId] = Object.assign(item, {
+        [conf.childrenField]: lookup[itemId][conf.childrenField]
+      })
     }
 
     const treeItem = lookup[itemId];
diff --git a/tslint.json b/tslint.json
index 7a03cfd..b815d9a 100644
--- a/tslint.json
+++ b/tslint.json
@@ -1,6 +1,7 @@
 {
   "extends": ["tslint:latest", "tslint-config-prettier"],
   "rules": {
-    "no-implicit-dependencies": [true, "dev"]
+    "no-implicit-dependencies": [true, "dev"],
+    "prefer-object-spread": false
   }
 }