diff --git a/src/datasets/utils/tf_utils.py b/src/datasets/utils/tf_utils.py
index 2de35a943e7..154f4d61072 100644
--- a/src/datasets/utils/tf_utils.py
+++ b/src/datasets/utils/tf_utils.py
@@ -278,7 +278,7 @@ def __init__(
         self.cols_to_retain = cols_to_retain
         self.collate_fn = collate_fn
         self.collate_fn_args = collate_fn_args
-        self.string_columns = [col for col, dtype in columns_to_np_types.items() if dtype in (np.unicode_, np.str_)]
+        self.string_columns = [col for col, dtype in columns_to_np_types.items() if dtype is np.str_]
         # Strings will be converted to arrays of single unicode chars, so that we can have a constant itemsize
         self.columns_to_np_types = {
             col: dtype if col not in self.string_columns else np.dtype("U1")