diff --git a/aioairzone/common.py b/aioairzone/common.py
index ca6581a..5069273 100644
--- a/aioairzone/common.py
+++ b/aioairzone/common.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from enum import Enum, IntEnum
+import json
 from typing import Any
 
 
@@ -234,3 +235,10 @@ def __str__(self) -> str:
 def get_system_zone_id(system_id: int, zone_id: int) -> str:
     """Combine system and zone IDs."""
     return f"{system_id}:{zone_id}"
+
+
+def json_dumps(data: Any) -> Any:
+    """Convert data to JSON."""
+    if data is not None:
+        return json.dumps(data)
+    return None
diff --git a/aioairzone/localapi.py b/aioairzone/localapi.py
index 9b79036..2f7f9b2 100644
--- a/aioairzone/localapi.py
+++ b/aioairzone/localapi.py
@@ -6,7 +6,6 @@
 from asyncio import Lock, Semaphore
 from dataclasses import dataclass
 from enum import IntEnum
-import json
 from json import JSONDecodeError
 import logging
 from typing import Any, cast
@@ -14,7 +13,7 @@
 from aiohttp import ClientConnectorError, ClientSession, ClientTimeout
 from aiohttp.client_reqrep import ClientResponse
 
-from .common import OperationMode, get_system_zone_id
+from .common import OperationMode, get_system_zone_id, json_dumps
 from .const import (
     API_ACS_MAX_TEMP,
     API_ACS_MIN_TEMP,
@@ -183,7 +182,7 @@ async def http_request(
                 resp: ClientResponse = await self.aiohttp_session.request(
                     method,
                     f"http://{self.options.host}:{self.options.port}/{path}",
-                    data=json.dumps(data),
+                    data=json_dumps(data),
                     headers={"Content-Type": "text/json"},
                     timeout=self._api_timeout,
                 )