diff --git a/swh/scheduler/api/serializers.py b/swh/scheduler/api/serializers.py
--- a/swh/scheduler/api/serializers.py
+++ b/swh/scheduler/api/serializers.py
@@ -13,7 +13,7 @@
 
 
 def _encode_model_object(obj):
-    d = attr.asdict(obj)
+    d = attr.asdict(obj, recurse=False)
     d["__type__"] = type(obj).__name__
     return d