diff --git a/retweetbot.py b/retweetbot.py
index f75fe60..21c77f4 100644
--- a/retweetbot.py
+++ b/retweetbot.py
@@ -127,7 +127,7 @@ class RetweetBot(object):
             # these lines.
             except twitter.error.TwitterError:
                 print("[ERROR] probably you already retweeted this tweet.")
-                return None
+                return ()
             except requests.exceptions.ConnectionError:
                 print("[ERROR] Bad Connection.")
                 sleep(10)