diff --git a/custom_components/luxtronik/climate.py b/custom_components/luxtronik/climate.py
index d766615..b232b0f 100644
--- a/custom_components/luxtronik/climate.py
+++ b/custom_components/luxtronik/climate.py
@@ -319,7 +319,7 @@ async def async_turn_off(self) -> None:
         await self.async_set_hvac_mode(HVACMode.OFF)
     
     async def async_turn_on(self) -> None:
-        await self.async_set_hvac_mode(HVACMode[self.entity_description.hvac_mode_mapping[LuxMode.automatic.value]])
+        await self.async_set_hvac_mode(HVACMode[self.entity_description.hvac_mode_mapping[LuxMode.automatic.value].upper()])
         
     async def async_set_hvac_mode(self, hvac_mode: HVACMode) -> None:
         """Set new target hvac mode."""