diff --git a/mas2ff2.py b/mas2ff2.py
index ea468b7..7e053b2 100644
--- a/mas2ff2.py
+++ b/mas2ff2.py
@@ -129,8 +129,7 @@ def run(instance, access_token, fanfou_cookie, fanfou_token):
     # first time run
     posted_ids = []
     # if file not exist, create it
-    with open('last_id.txt', 'a+') as f:
-      f.seek(0)
+    with open('last_id.txt', 'r') as f:
       # read lines
       posted_ids = f.readlines()
       # remove \n
@@ -164,6 +163,9 @@ def run(instance, access_token, fanfou_cookie, fanfou_token):
       if statuses:
         min_id = statuses[-1]['id']
       else:
+        if min_id:
+          with open('last_id.txt', 'a') as f:
+            f.write(str(min_id) + '\n')
         min_id = None
 
 if __name__ == '__main__':