diff --git a/backend/open_webui/utils/payload.py b/backend/open_webui/utils/payload.py
index f1befc53a8..962c98696f 100644
--- a/backend/open_webui/utils/payload.py
+++ b/backend/open_webui/utils/payload.py
@@ -328,12 +328,19 @@ def convert_chat_completions_messages_to_ollama(messages: list[dict]) -> list[di
             # If tool calls are present, add them to the message
             ollama_tool_calls = []
             for tool_call in tool_calls:
+                arguments = tool_call.get('function', {}).get('arguments')
+                if isinstance(arguments, str):
+                    try:
+                        arguments = JSONCodec.loads(arguments)
+                    except JSONCodec.JSONDecodeError:
+                        arguments = {}
+
                 ollama_tool_call = {
                     'index': tool_call.get('index', 0),
                     'id': tool_call.get('id', None),
                     'function': {
                         'name': tool_call.get('function', {}).get('name', ''),
-                        'arguments': JSONCodec.loads(tool_call.get('function', {}).get('arguments', {})),
+                        'arguments': arguments if isinstance(arguments, dict) else {},
                     },
                 }
                 ollama_tool_calls.append(ollama_tool_call)