diff --git a/dlt/common/typing.py b/dlt/common/typing.py
index 05720fe7d9..bdd2b914dc 100644
--- a/dlt/common/typing.py
+++ b/dlt/common/typing.py
@@ -26,6 +26,7 @@
     IO,
     Iterator,
     Generator,
+    cast,
 )
 
 from typing_extensions import (
@@ -243,7 +244,7 @@ def get_all_types_of_class_in_union(hint: Type[Any], cls: Type[TAny]) -> List[Ty
     return [
         t
         for t in get_args(hint)
-        if inspect.isclass(t) and (issubclass(t, cls) or issubclass(cls, t))
+        if not is_typeddict(t) and inspect.isclass(t) and (issubclass(t, cls) or issubclass(cls, t))
     ]