diff --git a/DialogueStateTracker.py b/DialogueStateTracker.py
index 8394049..b3122e8 100644
--- a/DialogueStateTracker.py
+++ b/DialogueStateTracker.py
@@ -27,7 +27,7 @@ def default_state():
         'user_action': [],
         'system_action': [],
         'terminated': False,
-        'booked': []
+        'booked': {}
     }