diff --git a/ollama/_client.py b/ollama/_client.py
index f38cab9..7b55f29 100644
--- a/ollama/_client.py
+++ b/ollama/_client.py
@@ -7,6 +7,7 @@ import platform
 import urllib.parse
 from os import PathLike
 from pathlib import Path
+from copy import deepcopy
 from hashlib import sha256
 from base64 import b64encode, b64decode
 
@@ -164,6 +165,8 @@ class Client(BaseClient):
     if not model:
       raise RequestError('must provide a model')
 
+    messages = deepcopy(messages)
+
     for message in messages or []:
       if not isinstance(message, dict):
         raise TypeError('messages must be a list of Message or dict-like objects')
@@ -449,6 +452,8 @@ class AsyncClient(BaseClient):
     if not model:
       raise RequestError('must provide a model')
 
+    messages = deepcopy(messages)
+
     for message in messages or []:
       if not isinstance(message, dict):
         raise TypeError('messages must be a list of strings')