diff --git a/custom_components/solarman/services.py b/custom_components/solarman/services.py
index 940911c..42f4e3c 100644
--- a/custom_components/solarman/services.py
+++ b/custom_components/solarman/services.py
@@ -55,18 +55,16 @@ async def read_holding_registers(call: ServiceCall) -> int:
 
         register = call.data.get(SERVICES_PARAM_REGISTER)
         quantity = call.data.get(SERVICES_PARAM_QUANTITY)
+        result = {}
 
         try:
-            response = await inverter.call(CODE.READ_HOLDING_REGISTERS, register, quantity)
+            if (response := await inverter.call(CODE.READ_HOLDING_REGISTERS, register, quantity)) is not None:
+                for i in range(0, quantity):
+                    result[register + i] = response[i]
+
         except Exception as e:
             raise ServiceValidationError(e, translation_domain = DOMAIN, translation_key = "call_failed")
 
-        result = {}
-
-        if response:
-            for i in range(0, quantity):
-                result[register + i] = response[i]
-
         return result
 
     async def read_input_registers(call: ServiceCall) -> int:
@@ -81,18 +79,16 @@ async def read_input_registers(call: ServiceCall) -> int:
 
         register = call.data.get(SERVICES_PARAM_REGISTER)
         quantity = call.data.get(SERVICES_PARAM_QUANTITY)
+        result = {}
 
         try:
-            response = await inverter.call(CODE.READ_INPUT, register, quantity)
+            if (response := await inverter.call(CODE.READ_INPUT, register, quantity)) is not None:
+                for i in range(0, quantity):
+                    result[register + i] = response[i]
+
         except Exception as e:
             raise ServiceValidationError(e, translation_domain = DOMAIN, translation_key = "call_failed")
 
-        result = {}
-
-        if response:
-            for i in range(0, quantity):
-                result[register + i] = response[i]
-
         return result
 
     async def write_holding_register(call: ServiceCall) -> None:
@@ -110,8 +106,6 @@ async def write_holding_register(call: ServiceCall) -> None:
         except Exception as e:
             raise ServiceValidationError(e, translation_domain = DOMAIN, translation_key = "call_failed")
 
-        return
-
     async def write_multiple_holding_registers(call: ServiceCall) -> None:
         _LOGGER.debug(f"write_multiple_holding_registers: {call}")
 
@@ -127,8 +121,6 @@ async def write_multiple_holding_registers(call: ServiceCall) -> None:
         except Exception as e:
             raise ServiceValidationError(e, translation_domain = DOMAIN, translation_key = "call_failed")
 
-        return
-
     hass.services.async_register(
         DOMAIN, SERVICE_READ_HOLDING_REGISTERS, read_holding_registers, schema = vol.Schema(HEADER_SCHEMA | QUANTITY_SCHEMA), supports_response = SupportsResponse.OPTIONAL
     )