diff --git a/src/fairchem/core/datasets/base_dataset.py b/src/fairchem/core/datasets/base_dataset.py
index 9f8aac3d0..d0d789560 100644
--- a/src/fairchem/core/datasets/base_dataset.py
+++ b/src/fairchem/core/datasets/base_dataset.py
@@ -13,7 +13,6 @@
 from typing import (
     TYPE_CHECKING,
     Any,
-    NamedTuple,
     TypeVar,
 )
 
@@ -109,7 +108,7 @@ def _metadata(self) -> DatasetMetadata:
         metadata = DatasetMetadata(
             **{
                 field: np.concatenate([metadata[field] for metadata in metadata_npzs])
-                for field in metadata_npzs[0].keys()
+                for field in metadata_npzs[0]
             }
         )