diff --git a/docs/api/system-preferences.md b/docs/api/system-preferences.md
index 20c330460ec..8b181de5f9c 100644
--- a/docs/api/system-preferences.md
+++ b/docs/api/system-preferences.md
@@ -130,6 +130,8 @@ This is necessary for events such as `NSUserDefaultsDidChangeNotification`.
   * `userInfo` Record<String, unknown>
   * `object` String
 
+Returns `Number` - The ID of this subscription
+
 Same as `subscribeNotification`, but uses `NSWorkspace.sharedWorkspace.notificationCenter`.
 This is necessary for events such as `NSWorkspaceDidActivateApplicationNotification`.