diff --git a/subtask.py b/subtask.py
index d17cdd4..ed1a8ab 100644
--- a/subtask.py
+++ b/subtask.py
@@ -118,7 +118,9 @@ def calibrate_new(label, offset, run = True, run_speed = 3.5):
             break
         ret, box = filter.get(label)
     
-    error = (box[0][2] + box[0][0] - 320) / 2 + offset
+    # 如果超过二十帧跳出，则此时 box 为空值，需要再校验 ret
+    if ret is True:
+        error = (box[0][2] + box[0][0] - 320) / 2 + offset
     if abs(error) > 10 and run:
         if error > 0:
             by_cmd.send_speed_x(-run_speed)