diff --git a/example/ck_tile/18_hstu_attention/hstu_block_masking.hpp b/example/ck_tile/18_hstu_attention/hstu_block_masking.hpp
index 3c39b332a6..161b0cb5cb 100644
--- a/example/ck_tile/18_hstu_attention/hstu_block_masking.hpp
+++ b/example/ck_tile/18_hstu_attention/hstu_block_masking.hpp
@@ -64,7 +64,7 @@ struct HstuBlockMaskWithLocal
                 index_t x_start = max(0, i_y - max_attn_len);
                 index_t x_end   = min(i_y + YTile, max_uih_len);
 
-                return ck_tile::make_tuple(x_start, x_end);
+                return ck_tile::make_tuple(x_start - x_start % XTile, x_end);
             };
         };
     }