diff --git a/xk.py b/xk.py
index de8123d..5c6adb3 100644
--- a/xk.py
+++ b/xk.py
@@ -4,9 +4,11 @@
 import sys
 import userinfo
 import course
+import time
 
 timeout = 1
 base_url = 'gdjwgl.bjut.edu.cn'
+wait_time = 0.1
 
 
 def retry_post(retry, session, h_url, **kwargs):
@@ -163,3 +165,4 @@ def sel_course(session, course_name, course_number, viewstate, username, name):
             print(result)
             if result == 'Successfully selected!':
                 todo_course.remove(cur_course)
+        time.sleep(wait_time)