diff --git a/pyaptamer/datasets/dataclasses/_masked.py b/pyaptamer/datasets/dataclasses/_masked.py
index 53bf064b..8817d6c6 100644
--- a/pyaptamer/datasets/dataclasses/_masked.py
+++ b/pyaptamer/datasets/dataclasses/_masked.py
@@ -151,7 +151,7 @@ def __getitem__(self, index: int) -> tuple[Tensor, Tensor, Tensor, Tensor]:
         y = torch.tensor(self.y[index], dtype=torch.int64)
 
         x_masked = x.clone().detach()
-        y_masked = x.clone().detach()
+        y_masked = y.clone().detach()
 
         # non-padding positions (0 is padding)
         seq_len = torch.sum(x_masked > 0)