diff --git a/lib/isn.ex b/lib/isn.ex
index ba6c4c0..5a6390f 100644
--- a/lib/isn.ex
+++ b/lib/isn.ex
@@ -79,8 +79,6 @@ for module <- ~w(ISBN ISMN ISSN ISBN13 ISMN13 ISSN13 UPC EAN13) do
   ecto_type = module |> String.downcase() |> String.to_atom()
 
   defmodule module_name do
-    @behaviour Ecto.Type
-
     @moduledoc """
     Definition for the ISN.#{module} module.
 
@@ -96,6 +94,8 @@ for module <- ~w(ISBN ISMN ISSN ISBN13 ISMN13 ISSN13 UPC EAN13) do
         end
     """
 
+    use Ecto.Type
+
     def type, do: unquote(ecto_type)
 
     def cast(nil), do: :error