diff --git a/swh/loader/pypi/loader.py b/swh/loader/pypi/loader.py
--- a/swh/loader/pypi/loader.py
+++ b/swh/loader/pypi/loader.py
@@ -103,14 +103,17 @@
             snapshot (dict): Last snapshot for the visit
 
         Returns:
-            tuple artifact's filename, artifact's sha256
+            list of (filename, sha256) tuples.
 
         """
         revs = [rev['target'] for rev in last_snapshot['branches'].values()]
         known_revisions = self.storage.revision_get(revs)
+        ret = []
         for revision in known_revisions:
-            artifact = revision['metadata']['original_artifact']
-            yield artifact['filename'], artifact['sha256']
+            if 'original_artifact' in revision['metadata']:
+                artifact = revision['metadata']['original_artifact']
+                ret.append((artifact['filename'], artifact['sha256']))
+        return ret
 
     def _last_snapshot(self):
         """Retrieve the last snapshot