diff --git a/custom_components/plant/sensor.py b/custom_components/plant/sensor.py
index 735ab5d7..9997842d 100644
--- a/custom_components/plant/sensor.py
+++ b/custom_components/plant/sensor.py
@@ -211,7 +211,7 @@ async def async_added_to_hass(self) -> None:
         state = await self.async_get_last_state()
 
         # We do not restore the state for these they are read from the external sensor anyway
-        self._attr_native_value = STATE_UNKNOWN
+        self._attr_native_value = None
         if state:
             if "external_sensor" in state.attributes:
                 self.replace_external_sensor(state.attributes["external_sensor"])
@@ -450,9 +450,9 @@ async def async_update(self) -> None:
             if external_sensor:
                 self._attr_native_value = self.ppfd(external_sensor.state)
             else:
-                self._attr_native_value = STATE_UNKNOWN
+                self._attr_native_value = None
         else:
-            self._attr_native_value = STATE_UNKNOWN
+            self._attr_native_value = None
 
     @callback
     def state_changed(self, entity_id: str, new_state: str) -> None:
@@ -466,9 +466,9 @@ def state_changed(self, entity_id: str, new_state: str) -> None:
             if external_sensor:
                 self._attr_native_value = self.ppfd(external_sensor.state)
             else:
-                self._attr_native_value = STATE_UNKNOWN
+                self._attr_native_value = None
         else:
-            self._attr_native_value = STATE_UNKNOWN
+            self._attr_native_value = None
 
 
 class PlantTotalLightIntegral(IntegrationSensor):