diff --git a/src/openai/_base_client.py b/src/openai/_base_client.py
index d5f1ab0903..22d78db3c5 100644
--- a/src/openai/_base_client.py
+++ b/src/openai/_base_client.py
@@ -492,6 +492,14 @@ def _build_request(
 else:
 raise RuntimeError(f"Unexpected JSON data type, {type(json_data)}, cannot merge with `extra_body`")
 
+ 
+ # --- PATCH START (Normalize model name) ---
+ if isinstance(json_data, dict) and "model" in json_data:
+ if isinstance(json_data["model"], str):
+ json_data["model"] = json_data["model"].strip().lower()
+ # --- PATCH END ---
+
+ 
 headers = self._build_headers(options, retries_taken=retries_taken)
 params = _merge_mappings(self.default_query, options.params)
 content_type = headers.get("Content-Type")
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://patch-diff.githubusercontent.com/raw/openai/openai-python/pull/2633.diff">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://patch-diff.githubusercontent.com/raw/openai/openai-python/pull/2633.diff" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast" selected="selected">配色反転</option>
<option value="larger-text">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>