diff --git a/src/llmtuner/data/loader.py b/src/llmtuner/data/loader.py
index 41c12422..70beea05 100644
--- a/src/llmtuner/data/loader.py
+++ b/src/llmtuner/data/loader.py
@@ -59,6 +59,13 @@ def get_dataset(
                 dataset_name=data_path,
                 subset_name=data_name,
             ).to_hf_dataset()
+
+            def map_func(example):
+                # do something to example
+                example['input'] = example['input'] or ''
+                return example
+
+            dataset = dataset.ds_instance.map(map_func)
         else:
             dataset = load_dataset(
                 path=data_path,