diff --git a/core/learn/schema.py b/core/learn/schema.py
index 807cec3..86b0916 100644
--- a/core/learn/schema.py
+++ b/core/learn/schema.py
@@ -412,7 +412,8 @@ def _iter(self: DataLoader) -> Iterator[tensor_dict_type]:
             base = d.base_dataloader
             base.async_prefetch = loader.async_prefetch
             base.async_prefetch_factor = loader.async_prefetch_factor
-            base._get_iterator = loader._get_iterator
+            if base.async_prefetch:
+                base._get_iterator = loader._get_iterator
             td = type(d)
             iter_prepared = getattr(td, "_iter_prepared_", False)
             if not iter_prepared: