diff --git a/abl/utils/utils.py b/abl/utils/utils.py
index d6e45db..8f29a02 100644
--- a/abl/utils/utils.py
+++ b/abl/utils/utils.py
@@ -158,6 +158,8 @@ def tab_data_to_tuple(X, y, reasoning_result = 0):
     '''
     Convert a tabular data to a tuple by adding a dimension to each element of X and y. The tuple contains three elements: data, label, and reasoning result.
     '''
+    if X is None:
+        return None
     if len(X) != len(y):
         raise ValueError("The length of X and y should be the same, but got {} and {}.".format(len(X), len(y)))
     return ([[x] for x in X], [[y_item] for y_item in y], [reasoning_result] * len(y))
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