diff --git a/lib/arc_ecto/definition.ex b/lib/arc_ecto/definition.ex
index 954c2cb..6978978 100644
--- a/lib/arc_ecto/definition.ex
+++ b/lib/arc_ecto/definition.ex
@@ -10,7 +10,7 @@ defmodule Arc.Ecto.Definition do
           @behaviour Ecto.Type
         end
 
-        @type t() :: String.t()
+        @type t() :: Arc.Ecto.t()
 
         def type, do: Arc.Ecto.Type.type()
         def cast(value), do: Arc.Ecto.Type.cast(unquote(definition), value)