diff --git a/Chapter3/1. Object Orientation/3.1.ts b/Chapter3/1. Object Orientation/3.1.ts
index 355cf7f..db0d9d1 100644
--- a/Chapter3/1. Object Orientation/3.1.ts	
+++ b/Chapter3/1. Object Orientation/3.1.ts	
@@ -2,7 +2,7 @@ declare var fs: any;
 
 interface FileItem {
     path: string;
-    contents: string[];
+    contents: FileItem[];
 }
 
 class FileReaderExample {