diff --git a/src/service/dialog_state_monitor.py b/src/service/dialog_state_monitor.py
index 6916229..b5bea59 100644
--- a/src/service/dialog_state_monitor.py
+++ b/src/service/dialog_state_monitor.py
@@ -9,7 +9,7 @@ def normalize(value):
     return ' '.join(value.split())
 
 
-class DialogStateMonitor:
+class DialogStateMonitor(DST):
     def __init__(self, initial_state_file: str = '../attributes.json'):
         DST.__init__(self)
         with open(initial_state_file) as file: