diff --git a/src/dbus_fast/service.py b/src/dbus_fast/service.py
index 0eff2b7..57e5cc4 100644
--- a/src/dbus_fast/service.py
+++ b/src/dbus_fast/service.py
@@ -504,7 +504,7 @@ class ServiceInterface:
 
     @staticmethod
     def _fn_result_to_body(
-        result: Optional[List[Any]],
+        result: Optional[Any],
         signature_tree: SignatureTree,
         replace_fds: bool = True,
     ) -> Tuple[List[Any], List[int]]: