diff --git a/homeassistant/components/mystrom/binary_sensor.py b/homeassistant/components/mystrom/binary_sensor.py
index 66ea2cc9679..17a1da75a96 100644
--- a/homeassistant/components/mystrom/binary_sensor.py
+++ b/homeassistant/components/mystrom/binary_sensor.py
@@ -67,6 +67,7 @@ class MyStromView(HomeAssistantView):
         else:
             new_state = self.buttons[entity_id].state == "off"
             self.buttons[entity_id].async_on_update(new_state)
+        return None
 
 
 class MyStromBinarySensor(BinarySensorEntity):