diff --git a/index.d.ts b/index.d.ts
index f2cf962..5e97ff9 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -7,7 +7,7 @@ interface IObj {
 declare function directoryTree<
   TCustomFile extends IObj = IObj,
   TCustomDir extends IObj = IObj,
-  TCustomResult = TCustomFile & TCustomDir
+  TCustomResult extends IObj = TCustomFile & TCustomDir
 >(
   path: string,
   options?: directoryTree.DirectoryTreeOptions,