diff --git a/neptyne_kernel/json_tools.py b/neptyne_kernel/json_tools.py
index 20d9644..2e6c432 100644
--- a/neptyne_kernel/json_tools.py
+++ b/neptyne_kernel/json_tools.py
@@ -16,14 +16,13 @@ def json_clean(obj: Any) -> dict:
 def json_default(obj: Any) -> str | int | list | float | None:
     if isinstance(obj, Empty):
         return None
+    if hasattr(obj, "__json__"):
+        return obj.__json__()
     try:
         from jupyter_client.jsonutil import json_default as jupyter_json_default
     except ImportError:
         from jupyter_client.jsonutil import date_default as jupyter_json_default
 
-    if hasattr(obj, "__json__"):
-        obj = obj.__json__()
-
     return jupyter_json_default(obj)
 
 
diff --git a/neptyne_kernel/widgets/register_widget_test.py b/neptyne_kernel/widgets/register_widget_test.py
index a17833d..8066a99 100644
--- a/neptyne_kernel/widgets/register_widget_test.py
+++ b/neptyne_kernel/widgets/register_widget_test.py
@@ -4,6 +4,7 @@
 from typing import Callable
 
 from ..cell_range import CellRange
+from ..json_tools import json_default
 from ..neptyne_protocol import WidgetParamType
 from ..util import list_like
 from .base_widget import BaseWidget
@@ -115,7 +116,7 @@ def test_register_widget():
 def test_widgets_with_enums_can_serialize():
     scatter = Scatter(x=[1, 2, 3], y=[4, 5, 6], trendline=Scatter.TrendlineType.POLY)
 
-    s = json.dumps(scatter)
+    s = json.dumps(scatter, default=json_default)
     scatter2 = Scatter(**json.loads(s))
 
     assert scatter2.trendline == Scatter.TrendlineType.POLY