diff --git a/controller/state/changer.py b/controller/state/changer.py
index 2896315..2e2c1c8 100644
--- a/controller/state/changer.py
+++ b/controller/state/changer.py
@@ -24,7 +24,7 @@ class Changer(object):
             'closed': self.close_in_valve
         }
 
-    def safe_remote_state(key):
+    def safe_remote_state(self, key):
         if key in ['out_valve', 'in_valve']:
             return self.remote_state.get(key, 'closed')
         else: