diff --git a/swh/journal/pytest_plugin.py b/swh/journal/pytest_plugin.py
--- a/swh/journal/pytest_plugin.py
+++ b/swh/journal/pytest_plugin.py
@@ -91,9 +91,6 @@
             continue
 
         for value in known_values:
-            if object_type == "origin_visit":
-                value["date"] = str(value["date"])
-
             assert value in received_values, (
                 f"expected {object_type} value {value!r} is "
                 "absent from consumed messages"
diff --git a/swh/journal/writer/kafka.py b/swh/journal/writer/kafka.py
--- a/swh/journal/writer/kafka.py
+++ b/swh/journal/writer/kafka.py
@@ -200,9 +200,6 @@
         self, object_type: str, object_: ModelObject
     ) -> Dict[str, str]:
         dict_ = object_.to_dict()
-        if object_type == "origin_visit":
-            # :(
-            dict_["date"] = str(dict_["date"])
         if object_type == "content":
             dict_.pop("data", None)
         return dict_