diff --git a/src/pv_controller/ToDevices.py b/src/pv_controller/ToDevices.py
index 55f221c..2afcb5e 100644
--- a/src/pv_controller/ToDevices.py
+++ b/src/pv_controller/ToDevices.py
@@ -24,7 +24,7 @@ class ToDevices(AbstractMqttPublisher):
                     continue
                 if device.register_type != 'coil':
                     raise Exception(f"Unsupported register type {device.register_type} for input device {device.name}")
-                value = payload == b'On'
+                value = payload == b'on'
                 self.modbusHandler.writeCoil(device.slave_id, device.address, value)
         except Exception as e:
             logger.error(f"Caught exception in onMessage: {str(e)}")