diff --git a/shared/sx/primitives_io.py b/shared/sx/primitives_io.py
index 02ad8f1..bb9e65a 100644
--- a/shared/sx/primitives_io.py
+++ b/shared/sx/primitives_io.py
@@ -225,7 +225,10 @@ def _dto_to_dict(obj: Any) -> dict[str, Any]:
     keys for any datetime-valued field so sx handlers can build URL paths
     without parsing date strings.
     """
-    if hasattr(obj, "_asdict"):
+    if hasattr(obj, "__dataclass_fields__"):
+        import dataclasses
+        d = dataclasses.asdict(obj)
+    elif hasattr(obj, "_asdict"):
         d = dict(obj._asdict())
     elif hasattr(obj, "__dict__"):
         d = {k: v for k, v in obj.__dict__.items() if not k.startswith("_")}