diff --git a/lib/pigeon.ex b/lib/pigeon.ex
index a02921ea..6f2c6e71 100644
--- a/lib/pigeon.ex
+++ b/lib/pigeon.ex
@@ -25,7 +25,7 @@ defmodule Pigeon do
   See `Pigeon.Adapter` for instructions.
   """
 
-  alias Pigeon.Tasks
+  alias Pigeon.{ADM, APNS, FCM, LegacyFCM, Tasks}
 
   @default_timeout 5_000
 
@@ -53,7 +53,11 @@ defmodule Pigeon do
           | {module, atom}
           | {module, atom, [any]}
 
-  @type notification :: %{__meta__: Pigeon.Metadata.t()}
+  @type notification ::
+          %ADM.Notification{}
+          | %APNS.Notification{}
+          | %FCM.Notification{}
+          | %LegacyFCM.Notification{}
 
   @typedoc ~S"""
   Options for sending push notifications.