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
@@ -114,6 +114,8 @@
         known_revisions = self.storage.revision_get(revs)
         ret = {}
         for revision in known_revisions:
+            if not revision:  # revision_get can return None
+                continue
             if 'original_artifact' in revision['metadata']:
                 artifact = revision['metadata']['original_artifact']
                 ret[artifact['filename'], artifact['sha256']] = revision['id']