diff --git a/example/ex2-mongoose.js b/example/ex2-mongoose.js
index 5eec629..572b4a8 100644
--- a/example/ex2-mongoose.js
+++ b/example/ex2-mongoose.js
@@ -10,7 +10,7 @@ db.once('open', function() {});
 
 // Define a simple schema
 const kittySchema = new mongoose.Schema({
-  _id: Schema.Types.Mixed,
+  _id: Buffer,
   name: String,
 });
 const Kitten = mongoose.model('Kitten', kittySchema);