diff --git a/swh/journal/writer/inmemory.py b/swh/journal/writer/inmemory.py
--- a/swh/journal/writer/inmemory.py
+++ b/swh/journal/writer/inmemory.py
@@ -7,10 +7,9 @@
 from multiprocessing import Manager
 from typing import List
 
+from swh.journal.serializers import ModelObject
 from swh.model.model import BaseModel
 
-from .kafka import ModelObject
-
 logger = logging.getLogger(__name__)