diff --git a/swh/journal/tests/conftest.py b/swh/journal/tests/conftest.py
--- a/swh/journal/tests/conftest.py
+++ b/swh/journal/tests/conftest.py
@@ -10,6 +10,7 @@
 import string
 
 from confluent_kafka import Consumer
+from hypothesis.strategies import one_of
 from subprocess import Popen
 from typing import Any, Dict, List, Optional, Tuple
 
@@ -18,6 +19,7 @@
     make_zookeeper_process, make_kafka_server, ZOOKEEPER_CONFIG_TEMPLATE,
 )
 
+from swh.model import hypothesis_strategies as strategies
 from swh.model.hashutil import hash_to_bytes
 
 
@@ -75,7 +77,7 @@
             'microseconds': 0,
         },
         'offset': 120,
-        'negative_utc': None,
+        'negative_utc': False,
     },
     {
         'timestamp': {
@@ -83,7 +85,7 @@
             'microseconds': 0,
         },
         'offset': 120,
-        'negative_utc': None,
+        'negative_utc': False,
     }
 ]
 
@@ -96,7 +98,7 @@
         'author':  COMMITTERS[0],
         'committer_date': DATES[0],
         'type': 'git',
-        'directory': '\x01'*20,
+        'directory': b'\x01'*20,
         'synthetic': False,
         'metadata': None,
         'parents': [],
@@ -109,7 +111,7 @@
         'author':  COMMITTERS[1],
         'committer_date': DATES[1],
         'type': 'hg',
-        'directory': '\x02'*20,
+        'directory': b'\x02'*20,
         'synthetic': False,
         'metadata': None,
         'parents': [],
@@ -126,7 +128,7 @@
                 'microseconds': 0,
             },
             'offset': 120,
-            'negative_utc': None,
+            'negative_utc': False,
         },
         'author': COMMITTERS[0],
         'target_type': 'revision',
@@ -262,3 +264,24 @@
     yield consumer
 
     consumer.close()
+
+
+def objects_d():
+    return one_of(
+        strategies.origins().map(
+            lambda x: ('origin', x.to_dict())),
+        strategies.origin_visits().map(
+            lambda x: ('origin_visit', x.to_dict())),
+        strategies.snapshots().map(
+            lambda x: ('snapshot', x.to_dict())),
+        strategies.releases().map(
+            lambda x: ('release', x.to_dict())),
+        strategies.revisions().map(
+            lambda x: ('revision', x.to_dict())),
+        strategies.directories().map(
+            lambda x: ('directory', x.to_dict())),
+        strategies.skipped_contents().map(
+            lambda x: ('skipped_content', x.to_dict())),
+        strategies.present_contents().map(
+            lambda x: ('content', x.to_dict())),
+    )
diff --git a/swh/journal/tests/test_write_replay.py b/swh/journal/tests/test_write_replay.py
--- a/swh/journal/tests/test_write_replay.py
+++ b/swh/journal/tests/test_write_replay.py
@@ -10,9 +10,7 @@
 from hypothesis import given, settings, HealthCheck
 from hypothesis.strategies import lists
 
-from swh.model.hypothesis_strategies import (
-    object_dicts, present_contents
-)
+from swh.model.hypothesis_strategies import present_contents
 from swh.model.model import Origin
 from swh.storage import get_storage
 from swh.storage.exc import HashCollision
@@ -22,7 +20,7 @@
 )
 
 from .utils import MockedJournalClient, MockedKafkaWriter
-
+from .conftest import objects_d
 
 storage_config = {
     'cls': 'memory',
@@ -56,7 +54,7 @@
     return rev_or_rel
 
 
-@given(lists(object_dicts(), min_size=1))
+@given(lists(objects_d(), min_size=1))
 @settings(suppress_health_check=[HealthCheck.too_slow])
 def test_write_replay_same_order_batches(objects):
     queue = []