diff --git a/src/llamafactory/data/collator.py b/src/llamafactory/data/collator.py
index 91871eaa..c878dcd3 100644
--- a/src/llamafactory/data/collator.py
+++ b/src/llamafactory/data/collator.py
@@ -41,7 +41,7 @@ def prepare_4d_attention_mask(attention_mask_with_indices: "torch.Tensor", dtype
                 [x, x, o, x, x, x],
                 [x, x, o, o, x, x],
                 [x, x, o, o, o, x],
-                [x, x, o, x, x, x],
+                [x, x, x, x, x, x],
             ]
         ]
     ]