diff --git a/goodwe/es.py b/goodwe/es.py
index f9d378d..13765f9 100644
--- a/goodwe/es.py
+++ b/goodwe/es.py
@@ -291,13 +291,18 @@ async def get_operation_modes(self, include_emulated: bool) -> Tuple[OperationMo
         return tuple(result)
 
     async def get_operation_mode(self) -> OperationMode:
-        mode = OperationMode(await self.read_setting('work_mode'))
+        mode_id = await self.read_setting('work_mode')
+        try:
+            mode = OperationMode(mode_id)
+        except ValueError:
+            logger.debug("Unknown work_mode value %d", mode_id)
+            return None
         if OperationMode.ECO != mode:
             return mode
-        ecomode = await self.read_setting('eco_mode_1')
-        if ecomode.is_eco_charge_mode():
+        eco_mode = await self.read_setting('eco_mode_1')
+        if eco_mode.is_eco_charge_mode():
             return OperationMode.ECO_CHARGE
-        elif ecomode.is_eco_discharge_mode():
+        elif eco_mode.is_eco_discharge_mode():
             return OperationMode.ECO_DISCHARGE
         else:
             return OperationMode.ECO
diff --git a/goodwe/et.py b/goodwe/et.py
index 8cbca66..dd202ce 100644
--- a/goodwe/et.py
+++ b/goodwe/et.py
@@ -616,13 +616,18 @@ async def get_operation_modes(self, include_emulated: bool) -> Tuple[OperationMo
         return tuple(result)
 
     async def get_operation_mode(self) -> OperationMode:
-        mode = OperationMode(await self.read_setting('work_mode'))
+        mode_id = await self.read_setting('work_mode')
+        try:
+            mode = OperationMode(mode_id)
+        except ValueError:
+            logger.debug("Unknown work_mode value %d", mode_id)
+            return None
         if OperationMode.ECO != mode:
             return mode
-        ecomode = await self.read_setting('eco_mode_1')
-        if ecomode.is_eco_charge_mode():
+        eco_mode = await self.read_setting('eco_mode_1')
+        if eco_mode.is_eco_charge_mode():
             return OperationMode.ECO_CHARGE
-        elif ecomode.is_eco_discharge_mode():
+        elif eco_mode.is_eco_discharge_mode():
             return OperationMode.ECO_DISCHARGE
         else:
             return OperationMode.ECO