diff --git a/calamari_ocr/ocr/dataset/data.py b/calamari_ocr/ocr/dataset/data.py
index 2f46fdce..6e16e2f3 100644
--- a/calamari_ocr/ocr/dataset/data.py
+++ b/calamari_ocr/ocr/dataset/data.py
@@ -88,6 +88,7 @@ def _target_layer_specs(self):
     def element_length_fn(self) -> Callable[[Dict[str, AnyTensor]], AnyTensor]:
         def img_len(x):
             return x["img_len"]
+
         return img_len
 
     def create_pipeline(