diff --git a/custom_components/petlibro/devices/feeders/polar_wet_food_feeder.py b/custom_components/petlibro/devices/feeders/polar_wet_food_feeder.py
index 6f7729d..da8dd8c 100644
--- a/custom_components/petlibro/devices/feeders/polar_wet_food_feeder.py
+++ b/custom_components/petlibro/devices/feeders/polar_wet_food_feeder.py
@@ -35,6 +35,11 @@ async def refresh(self):
     def battery_state(self) -> str | None:
         return self._data.get("batteryState")
 
+    @property
+    def device_sn(self) -> str:
+        """Returns the serial number of the device."""
+        return self._data.get("deviceSn", "unknown")
+
     @property
     def door_blocked(self) -> bool | None:
         return self._data.get("realInfo", {}).get("barnDoorError")
diff --git a/custom_components/petlibro/sensor.py b/custom_components/petlibro/sensor.py
index 37412cb..a2a0991 100644
--- a/custom_components/petlibro/sensor.py
+++ b/custom_components/petlibro/sensor.py
@@ -543,7 +543,7 @@ def device_class(self) -> SensorDeviceClass | None:
     ],
     PolarWetFoodFeeder: [
         PetLibroSensorEntityDescription[PolarWetFoodFeeder](
-            key="serial",
+            key="device_sn",
             translation_key="device_sn",
             icon="mdi:identifier",
             name="Device SN"