diff --git a/utils/utils.py b/utils/utils.py
index 3b72bbbc..e8c83613 100755
--- a/utils/utils.py
+++ b/utils/utils.py
@@ -506,15 +506,15 @@ def non_max_suppression(prediction, conf_thres=0.5, nms_thres=0.5, multi_cls=Tru
             continue
 
         # Box (center x, center y, width, height) to (x1, y1, x2, y2)
-        pred[:, :4] = xywh2xyxy(pred[:, :4])
+        box = xywh2xyxy(pred[:, :4])
 
-        # Multi-class
+        # Detections matrix nx6 (xyxy, conf, cls)
         if multi_cls or conf_thres < 0.01:
             i, j = (pred[:, 5:] > conf_thres).nonzero().t()
-            pred = torch.cat((pred[i, :4], pred[i, j + 5].unsqueeze(1), j.float().unsqueeze(1)), 1)
+            pred = torch.cat((box[i], pred[i, j + 5].unsqueeze(1), j.float().unsqueeze(1)), 1)
         else:  # best class only
             conf, j = pred[:, 5:].max(1)
-            pred = torch.cat((pred[:, :4], conf.unsqueeze(1), j.float().unsqueeze(1)), 1)  # (xyxy, conf, cls)
+            pred = torch.cat((box, conf.unsqueeze(1), j.float().unsqueeze(1)), 1)
 
         # Apply finite constraint
         pred = pred[torch.isfinite(pred).all(1)]