diff --git a/swh/indexer/metadata.py b/swh/indexer/metadata.py
--- a/swh/indexer/metadata.py
+++ b/swh/indexer/metadata.py
@@ -147,7 +147,12 @@
 
         try:
             root_dir = rev['directory']
-            dir_ls = self.storage.directory_ls(root_dir, recursive=False)
+            dir_ls = list(self.storage.directory_ls(root_dir, recursive=False))
+            if [entry['type'] for entry in dir_ls] == ['dir']:
+                # If the root is just a single directory, recurse into it
+                # eg. PyPI packages, GNU tarballs
+                subdir = dir_ls[0]['target']
+                dir_ls = self.storage.directory_ls(subdir, recursive=False)
             files = [entry for entry in dir_ls if entry['type'] == 'file']
             detected_files = detect_metadata(files)
             (mappings, metadata) = self.translate_revision_intrinsic_metadata(
diff --git a/swh/indexer/tests/test_metadata.py b/swh/indexer/tests/test_metadata.py
--- a/swh/indexer/tests/test_metadata.py
+++ b/swh/indexer/tests/test_metadata.py
@@ -1135,3 +1135,61 @@
 
         # then
         self.assertEqual(expected_results, results)
+
+    def test_revision_metadata_indexer_single_root_dir(self):
+        metadata_indexer = RevisionMetadataIndexer(
+            config=REVISION_METADATA_CONFIG)
+        fill_obj_storage(metadata_indexer.objstorage)
+        fill_storage(metadata_indexer.storage)
+
+        # Add a parent directory, that is the only directory at the root
+        # of the revision
+        rev_id = hash_to_bytes('8dbb6aeb036e7fd80664eb8bfd1507881af1ba9f')
+        subdir_id = metadata_indexer.storage._revisions[rev_id]['directory']
+        metadata_indexer.storage._revisions[rev_id]['directory'] = b'123456'
+        metadata_indexer.storage.directory_add([{
+            'id': b'123456',
+            'entries': [{
+                'target': subdir_id,
+                'type': 'dir',
+                'length': None,
+                'name': b'foobar-1.0.0',
+                'sha1': None,
+                'perms': 16384,
+                'sha1_git': None,
+                'status': None,
+                'sha256': None
+            }],
+        }])
+
+        tool = metadata_indexer.idx_storage.indexer_configuration_get(
+            {'tool_'+k: v for (k, v) in TRANSLATOR_TOOL.items()})
+        assert tool is not None
+
+        metadata_indexer.idx_storage.content_metadata_add([{
+            'indexer_configuration_id': tool['id'],
+            'id': b'cde',
+            'metadata': YARN_PARSER_METADATA,
+        }])
+
+        sha1_gits = [
+            hash_to_bytes('8dbb6aeb036e7fd80664eb8bfd1507881af1ba9f'),
+        ]
+        metadata_indexer.run(sha1_gits, 'update-dups')
+
+        results = list(
+            metadata_indexer.idx_storage.
+            revision_intrinsic_metadata_get(sha1_gits))
+
+        expected_results = [{
+            'id': hash_to_bytes('8dbb6aeb036e7fd80664eb8bfd1507881af1ba9f'),
+            'tool': TRANSLATOR_TOOL,
+            'metadata': YARN_PARSER_METADATA,
+            'mappings': ['npm'],
+        }]
+
+        for result in results:
+            del result['tool']['id']
+
+        # then
+        self.assertEqual(expected_results, results)