diff --git a/swh/storage/validate.py b/swh/storage/validate.py
index 217f5303..cf275ad2 100644
--- a/swh/storage/validate.py
+++ b/swh/storage/validate.py
@@ -1,101 +1,101 @@
 # Copyright (C) 2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import datetime
 import contextlib
 from typing import Dict, Iterable, List, Union
 
 from swh.model.model import (
     BaseModel, SkippedContent, Content, Directory, Revision, Release, Snapshot,
     OriginVisit, Origin
 )
 
 from . import get_storage
 from .exc import StorageArgumentException
 
 
 VALIDATION_EXCEPTIONS = (
     KeyError,
     TypeError,
     ValueError,
 )
 
 
 @contextlib.contextmanager
 def convert_validation_exceptions():
     """Catches validation errors arguments, and re-raises a
     StorageArgumentException."""
     try:
         yield
     except VALIDATION_EXCEPTIONS as e:
-        raise StorageArgumentException(*e.args)
+        raise StorageArgumentException(str(e))
 
 
 class ValidatingProxyStorage:
     """Storage implementation converts dictionaries to swh-model objects
     before calling its backend, and back to dicts before returning results
 
     """
     def __init__(self, storage):
         self.storage = get_storage(**storage)
 
     def __getattr__(self, key):
         if key == 'storage':
             raise AttributeError(key)
         return getattr(self.storage, key)
 
     def content_add(self, content: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             contents = [Content.from_dict(c) for c in content]
         return self.storage.content_add(contents)
 
     def content_add_metadata(self, content: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             contents = [Content.from_dict(c) for c in content]
         return self.storage.content_add_metadata(contents)
 
     def skipped_content_add(self, content: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             contents = [SkippedContent.from_dict(c) for c in content]
         return self.storage.skipped_content_add(contents)
 
     def directory_add(self, directories: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             directories = [Directory.from_dict(d) for d in directories]
         return self.storage.directory_add(directories)
 
     def revision_add(self, revisions: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             revisions = [Revision.from_dict(r) for r in revisions]
         return self.storage.revision_add(revisions)
 
     def release_add(self, releases: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             releases = [Release.from_dict(r) for r in releases]
         return self.storage.release_add(releases)
 
     def snapshot_add(self, snapshots: Iterable[Dict]) -> Dict:
         with convert_validation_exceptions():
             snapshots = [Snapshot.from_dict(s) for s in snapshots]
         return self.storage.snapshot_add(snapshots)
 
     def origin_visit_add(
             self, origin_url: str,
             date: Union[datetime.datetime], type: str) -> Dict[str, BaseModel]:
         with convert_validation_exceptions():
             visit = OriginVisit(origin=origin_url, date=date, type=type,
                                 status='ongoing', snapshot=None)
         return self.storage.origin_visit_add(
             visit.origin, visit.date, visit.type)
 
     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)