diff --git a/yolort/models/box_head.py b/yolort/models/box_head.py
index 73bc0c90..50442daa 100644
--- a/yolort/models/box_head.py
+++ b/yolort/models/box_head.py
@@ -226,7 +226,7 @@ def build_targets(
         targets: Tensor,
         head_outputs: List[Tensor],
         anchor_grids: Tensor,
-    ) -> Tuple[List[Tensor], List[Tensor], List[Tuple[Tensor, Tensor, Tensor, Tensor]], List[Tensor],]:
+    ) -> Tuple[List[Tensor], List[Tensor], List[Tuple[Tensor, Tensor, Tensor, Tensor]], List[Tensor]]:
         device = targets.device
         num_anchors = self.num_anchors