diff --git a/yolox/utils/boxes.py b/yolox/utils/boxes.py
index dbe10d957..af4e09311 100644
--- a/yolox/utils/boxes.py
+++ b/yolox/utils/boxes.py
@@ -31,10 +31,10 @@ def filter_box(output, scale_range):
 
 def postprocess(prediction, num_classes, conf_thre=0.7, nms_thre=0.45, class_agnostic=False):
     box_corner = prediction.new(prediction.shape)
-    box_corner[:, :, 0] = prediction[:, :, 0] - prediction[:, :, 2] / 2
-    box_corner[:, :, 1] = prediction[:, :, 1] - prediction[:, :, 3] / 2
-    box_corner[:, :, 2] = prediction[:, :, 0] + prediction[:, :, 2] / 2
-    box_corner[:, :, 3] = prediction[:, :, 1] + prediction[:, :, 3] / 2
+    box_corner[:, :, 0] = torch.nn.functional.relu(prediction[:, :, 0] - prediction[:, :, 2] / 2)
+    box_corner[:, :, 1] = torch.nn.functional.relu(prediction[:, :, 1] - prediction[:, :, 3] / 2)
+    box_corner[:, :, 2] = torch.nn.functional.relu(prediction[:, :, 0] + prediction[:, :, 2] / 2)
+    box_corner[:, :, 3] = torch.nn.functional.relu(prediction[:, :, 1] + prediction[:, :, 3] / 2)
     prediction[:, :, :4] = box_corner[:, :, :4]
 
     output = [None for _ in range(len(prediction))]