diff --git a/swh/indexer/metadata_detector.py b/swh/indexer/metadata_detector.py
--- a/swh/indexer/metadata_detector.py
+++ b/swh/indexer/metadata_detector.py
@@ -17,6 +17,7 @@
         - empty list if nothing was found
         - dictionary {mapping_filenames[name]:f['sha1']}
     """
+    files = list(files)
     results = {}
     for (mapping_name, mapping) in MAPPINGS.items():
         matches = mapping.detect_metadata_files(files)