diff --git a/swh/loader/package/nixguix/tests/test_nixguix.py b/swh/loader/package/nixguix/tests/test_nixguix.py
--- a/swh/loader/package/nixguix/tests/test_nixguix.py
+++ b/swh/loader/package/nixguix/tests/test_nixguix.py
@@ -11,7 +11,7 @@
 
 from json.decoder import JSONDecodeError
 from swh.storage.interface import StorageInterface
-from typing import Any, Dict, Iterable, Optional, Tuple, Union
+from typing import Dict, Iterable, Optional, Tuple
 
 from unittest.mock import patch
 
@@ -53,7 +53,7 @@
 
 
 def check_snapshot(
-    snapshot: Union[Dict[str, Any], Snapshot],
+    snapshot: Snapshot,
     storage: StorageInterface,
     allowed_empty: Iterable[Tuple[TargetType, bytes]] = [
         (TargetType.REVISION, b"evaluation")
diff --git a/swh/loader/tests/__init__.py b/swh/loader/tests/__init__.py
--- a/swh/loader/tests/__init__.py
+++ b/swh/loader/tests/__init__.py
@@ -8,7 +8,7 @@
 
 from collections import defaultdict
 from pathlib import PosixPath
-from typing import Any, Dict, Iterable, List, Optional, Tuple, Union
+from typing import Dict, Iterable, List, Optional, Tuple, Union
 
 from swh.model.model import OriginVisitStatus, Snapshot, TargetType
 from swh.model.hashutil import hash_to_bytes
@@ -114,7 +114,7 @@
 
 
 def check_snapshot(
-    snapshot: Union[Dict[str, Any], Snapshot],
+    snapshot: Snapshot,
     storage: StorageInterface,
     allowed_empty: Iterable[Tuple[TargetType, bytes]] = [],
 ):
@@ -135,8 +135,6 @@
         needed.
 
     """
-    if isinstance(snapshot, dict):
-        snapshot = Snapshot.from_dict(snapshot)
     if not isinstance(snapshot, Snapshot):
         raise AssertionError(f"variable 'snapshot' must be a snapshot: {snapshot!r}")
 
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
@@ -347,11 +347,10 @@
         "snapshot:add": 1,
     }
 
-    for snap in [SNAPSHOT, SNAPSHOT.to_dict()]:
-        # all should be fine!
-        check_snapshot(
-            snap, swh_storage, allowed_empty=[(TargetType.REVISION, b"evaluation")]
-        )
+    # all should be fine!
+    check_snapshot(
+        SNAPSHOT, swh_storage, allowed_empty=[(TargetType.REVISION, b"evaluation")]
+    )
 
 
 def test_check_snapshot_failures(swh_storage):