diff --git a/src/axolotl/monkeypatch/flex_attn.py b/src/axolotl/monkeypatch/flex_attn.py
index 8089edeae..a1c2de644 100644
--- a/src/axolotl/monkeypatch/flex_attn.py
+++ b/src/axolotl/monkeypatch/flex_attn.py
@@ -51,7 +51,7 @@ def create_block_causal_mask(
         residue_len = max_seq_len - torch.sum(seq_lens[sample_idx])
         block_attn_masks.append(
             torch.tril(
-                torch.zeros(
+                torch.ones(
                     residue_len, residue_len, dtype=torch.bool, device=seq_lens[sample_idx].device
                 )
             )