diff --git a/ppdet/modeling/post_process.py b/ppdet/modeling/post_process.py
index cc5116ebaa5ba9486fb82a0b7b1b90ce4f16dd47..6ab9da6f4d67df01b7a4541130e78ba0fa6f9dee 100644
--- a/ppdet/modeling/post_process.py
+++ b/ppdet/modeling/post_process.py
@@ -90,7 +90,7 @@ class BBoxPostProcess(object):
         """
 
         if bboxes.shape[0] == 0:
-            bbox_pred = paddle.to_tensor(
+            bboxes = paddle.to_tensor(
                 np.array(
                     [[-1, 0.0, 0.0, 0.0, 0.0, 0.0]], dtype='float32'))
             bbox_num = paddle.to_tensor(np.array([1], dtype='int32'))