diff --git a/dlt/extract/resource.py b/dlt/extract/resource.py
index 5fb5b795b3..28a071729e 100644
--- a/dlt/extract/resource.py
+++ b/dlt/extract/resource.py
@@ -352,7 +352,10 @@ def parallelize(self) -> "DltResource":
         """
         if (
             not inspect.isgenerator(self._pipe.gen)
-            and not inspect.isgeneratorfunction(inspect.unwrap(self._pipe.gen))
+            and not (
+                callable(self._pipe.gen)
+                and inspect.isgeneratorfunction(inspect.unwrap(self._pipe.gen))
+            )
             and not (callable(self._pipe.gen) and self.is_transformer)
         ):
             raise InvalidParallelResourceDataType(self.name, self._pipe.gen, type(self._pipe.gen))