diff --git a/backend/open_webui/main.py b/backend/open_webui/main.py
index 47fbd7a73c..d4f72a3632 100644
--- a/backend/open_webui/main.py
+++ b/backend/open_webui/main.py
@@ -229,6 +229,7 @@ from open_webui.utils.chat_variables import (
     normalize_chat_variables,
 )
 from open_webui.utils.embeddings import generate_embeddings
+from open_webui.utils.json_codec import JSONCodec
 from open_webui.utils.json_response import apply_orjson_http_json
 from open_webui.utils.logger import start_logger
 from open_webui.utils.middleware import (
@@ -1842,7 +1843,7 @@ async def passthrough_anthropic_messages(request: Request, form_data: dict, user
         response = await session.request(
             method='POST',
             url=request_url,
-            data=json.dumps(payload),
+            data=JSONCodec.dumps(payload),
             headers=headers,
             cookies=cookies,
             ssl=AIOHTTP_CLIENT_SESSION_SSL,