diff --git a/homeassistant/components/melcloud/sensor.py b/homeassistant/components/melcloud/sensor.py
index ed64647071b..774b66ab67e 100644
--- a/homeassistant/components/melcloud/sensor.py
+++ b/homeassistant/components/melcloud/sensor.py
@@ -69,7 +69,7 @@ ATW_ZONE_SENSORS = {
     "flow_temperature": {
         ATTR_MEASUREMENT_NAME: "Flow Temperature",
         ATTR_ICON: "mdi:thermometer",
-        ATTR_UNIT_FN: lambda x: TEMP_UNIT_LOOKUP.get(x.device.temp_unit, TEMP_CELSIUS),
+        ATTR_UNIT: TEMP_CELSIUS,
         ATTR_DEVICE_CLASS: DEVICE_CLASS_TEMPERATURE,
         ATTR_VALUE_FN: lambda zone: zone.flow_temperature,
         ATTR_ENABLED_FN: lambda x: True,
@@ -77,7 +77,7 @@ ATW_ZONE_SENSORS = {
     "return_temperature": {
         ATTR_MEASUREMENT_NAME: "Flow Return Temperature",
         ATTR_ICON: "mdi:thermometer",
-        ATTR_UNIT_FN: lambda x: TEMP_UNIT_LOOKUP.get(x.device.temp_unit, TEMP_CELSIUS),
+        ATTR_UNIT: TEMP_CELSIUS,
         ATTR_DEVICE_CLASS: DEVICE_CLASS_TEMPERATURE,
         ATTR_VALUE_FN: lambda zone: zone.return_temperature,
         ATTR_ENABLED_FN: lambda x: True,