diff --git a/swh/journal/writer/inmemory.py b/swh/journal/writer/inmemory.py
index 175f473..297e0c2 100644
--- a/swh/journal/writer/inmemory.py
+++ b/swh/journal/writer/inmemory.py
@@ -1,33 +1,32 @@
 # Copyright (C) 2019 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
 
 import logging
-import copy
 
 from multiprocessing import Manager
 from typing import List
 
 from swh.model.model import BaseModel
 
 from .kafka import ModelObject
 
 logger = logging.getLogger(__name__)
 
 
 class InMemoryJournalWriter:
     def __init__(self):
         # Share the list of objects across processes, for RemoteAPI tests.
         self.manager = Manager()
         self.objects = self.manager.list()
 
     def write_addition(self, object_type: str, object_: ModelObject) -> None:
         assert isinstance(object_, BaseModel)
-        self.objects.append((object_type, copy.deepcopy(object_)))
+        self.objects.append((object_type, object_))
 
     write_update = write_addition
 
     def write_additions(self, object_type: str, objects: List[ModelObject]) -> None:
         for object_ in objects:
             self.write_addition(object_type, object_)