diff --git a/guides/concepts/resources.md b/guides/concepts/resources.md
index 5138962..d61f19e 100644
--- a/guides/concepts/resources.md
+++ b/guides/concepts/resources.md
@@ -1323,7 +1323,7 @@ Which means the following filters are required:
 {% highlight ruby %}
 class NoteResource < ApplicationResource
   attribute :notable_id, :integer, only: [:filterable]
-  attribute :notable_type, :string, only: [:filterable]
+  attribute :notable_type, :string_enum, only: [:filterable], allow: ['Employee']
   # ... code ...
 end
 {% endhighlight %}