diff --git a/dlt/extract/extract.py b/dlt/extract/extract.py
index a5cf6b3e72..56ec679e62 100644
--- a/dlt/extract/extract.py
+++ b/dlt/extract/extract.py
@@ -2,7 +2,7 @@
 from collections.abc import Sequence as C_Sequence
 from copy import copy
 import itertools
-from typing import Iterator, List, Dict, Any
+from typing import Iterator, List, Dict, Any, Optional
 import yaml
 
 from dlt.common.configuration.container import Container