diff --git a/swh/storage/validate.py b/swh/storage/validate.py
--- a/swh/storage/validate.py
+++ b/swh/storage/validate.py
@@ -4,7 +4,7 @@
 # See top-level LICENSE file for more information
 
 import contextlib
-from typing import Dict, Iterable, Iterator, List, Optional, Tuple
+from typing import Dict, Iterable, Iterator, List, Optional, Tuple, Union
 
 from swh.model.model import (
     SkippedContent,
@@ -42,6 +42,7 @@
     """Storage implementation converts dictionaries to swh-model objects
     before calling its backend, and back to dicts before returning results
 
+    For test purposes.
     """
 
     def __init__(self, storage):
@@ -113,15 +114,26 @@
     def origin_visit_add(self, visits: Iterable[OriginVisit]) -> Iterable[OriginVisit]:
         return self.storage.origin_visit_add(visits)
 
-    def origin_add(self, origins: Iterable[Dict]) -> List[Dict]:
-        with convert_validation_exceptions():
-            origins = [Origin.from_dict(o) for o in origins]
-        return self.storage.origin_add(origins)
-
-    def origin_add_one(self, origin: Dict) -> int:
-        with convert_validation_exceptions():
-            origin = Origin.from_dict(origin)
-        return self.storage.origin_add_one(origin)
+    def origin_add(self, origins: Union[Iterable[Dict], Iterable[Origin]]) -> List:
+        origins_: List[Origin] = []
+        for o in origins:
+            ori: Origin
+            if isinstance(o, Dict):
+                with convert_validation_exceptions():
+                    ori = Origin.from_dict(o)
+            else:
+                ori = o
+            origins_.append(ori)
+        return self.storage.origin_add(origins_)
+
+    def origin_add_one(self, origin: Union[Dict, Origin]) -> int:
+        origin_: Origin
+        if isinstance(origin, Dict):
+            with convert_validation_exceptions():
+                origin_ = Origin.from_dict(origin)
+        else:
+            origin_ = origin
+        return self.storage.origin_add_one(origin_)
 
     def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
         return self.storage.clear_buffers(object_types)