diff --git a/swh/scheduler/api/serializers.py b/swh/scheduler/api/serializers.py
index 930c700..354d301 100644
--- a/swh/scheduler/api/serializers.py
+++ b/swh/scheduler/api/serializers.py
@@ -1,28 +1,28 @@
 # Copyright (C) 2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 """Decoder and encoders for swh.scheduler.model objects."""
 
 from typing import Callable, Dict, List, Tuple
 
 import attr
 
 import swh.scheduler.model as model
 
 
 def _encode_model_object(obj):
-    d = attr.asdict(obj)
+    d = attr.asdict(obj, recurse=False)
     d["__type__"] = type(obj).__name__
     return d
 
 
 ENCODERS: List[Tuple[type, str, Callable]] = [
     (model.BaseSchedulerModel, "scheduler_model", _encode_model_object),
 ]
 
 
 DECODERS: Dict[str, Callable] = {
     "scheduler_model": lambda d: getattr(model, d.pop("__type__"))(**d)
 }