diff --git a/yolo/utils/bounding_box_utils.py b/yolo/utils/bounding_box_utils.py
index 20539be3..54eaae11 100644
--- a/yolo/utils/bounding_box_utils.py
+++ b/yolo/utils/bounding_box_utils.py
@@ -278,7 +278,7 @@ def __call__(self, target: Tensor, predict: Tuple[Tensor]) -> Tuple[Tensor, Tens
         topk_targets, topk_mask = self.filter_topk(target_matrix, topk=self.topk)
 
         # delete one anchor pred assign to mutliple gts
-        unique_indices, valid_mask, topk_mask = self.filter_duplicates(iou_mat, topk_mask)
+        unique_indices, valid_mask, topk_mask = self.filter_duplicates(topk_targets, topk_mask)
 
         align_bbox = torch.gather(target_bbox, 1, unique_indices.repeat(1, 1, 4))
         align_cls = torch.gather(target_cls, 1, unique_indices).squeeze(-1)