diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,5 +1,5 @@
 swh.core >= 0.3
-swh.model >= 3.1.0
+swh.model >= 4.3.0
 swh.objstorage >= 0.2.2
 swh.scheduler >= 0.4.0
 swh.storage >= 0.29.0
diff --git a/swh/loader/tests/test_init.py b/swh/loader/tests/test_init.py
--- a/swh/loader/tests/test_init.py
+++ b/swh/loader/tests/test_init.py
@@ -98,26 +98,14 @@
         email=b"nicolas@example.com",
         fullname=b"Nicolas Dandrimont <nicolas@example.com> ",
     ),
-    date=TimestampWithTimezone.from_datetime(
-        datetime.datetime(
-            2009,
-            2,
-            14,
-            1,
-            31,
-            30,
-            tzinfo=datetime.timezone(datetime.timedelta(seconds=7200)),
-        )
-    ),
+    date=TimestampWithTimezone(Timestamp(1234567890, 0), offset_bytes=b"+0200"),
     committer=Person(
         name=b"St\xc3fano Zacchiroli",
         email=b"stefano@example.com",
         fullname=b"St\xc3fano Zacchiroli <stefano@example.com>",
     ),
     committer_date=TimestampWithTimezone(
-        timestamp=Timestamp(seconds=1123456789, microseconds=0),
-        offset=0,
-        negative_utc=True,
+        Timestamp(1123456789, 0), offset_bytes=b"-0000"
     ),
     parents=(),
     type=RevisionType.GIT,