diff --git a/swh/indexer/indexer.py b/swh/indexer/indexer.py
--- a/swh/indexer/indexer.py
+++ b/swh/indexer/indexer.py
@@ -346,6 +346,8 @@
             **kwargs: passed to the `index` method
 
         """
+        ids = [hashutil.hash_to_bytes(id_) if isinstance(id_, str) else id_
+               for id_ in ids]
         results = []
         try:
             for sha1 in ids: