diff --git a/spaceapi/utils.py b/spaceapi/utils.py
--- a/spaceapi/utils.py
+++ b/spaceapi/utils.py
@@ -17,16 +17,16 @@ if not os.path.exists(default_json_file)
 elif not os.path.isfile(default_json_file):
     raise RuntimeError('default.json is not a file!')
 
-possible_open_tweets = {
+possible_open_tweets = (
     'The space is now open!',
     'The space is open! Come in and hack something!',
     'Yes, we\'re open! Come in and create something!',
-}
+)
 
-possible_closed_tweets = {
+possible_closed_tweets = (
     'The space is now closed!',
     'We\'re closed now! See you soon.',
-}
+)
 
 
 def send_tweet(tweet):