diff --git a/functions-common b/functions-common
index 37c1862c28..0ae51e3df1 100644
--- a/functions-common
+++ b/functions-common
@@ -440,7 +440,7 @@ function GetOSVersion {
 source /etc/os-release
 if [[ "${ID}" =~ (centos|rocky|rhel) ]]; then
 os_RELEASE=${VERSION_ID}
- os_CODENAME=$(echo $VERSION &#124; grep -oP '(?<=[(])[^)]*')
+ os_CODENAME=$(echo $VERSION &#124; grep -oP '(?<=[(])[^)]*' &#124;&#124; echo 'n/a')
 os_VENDOR=$(echo $NAME &#124; tr -d '[:space:]')
 else
 _ensure_lsb_release
</div><div class="naked_ctrl">
<form action="/index.cgi/speech" 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://opendev.org/openstack/devstack/commit/f09da620cb5973f9a77233a700b06612462678e5.diff">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://opendev.org/openstack/devstack/commit/f09da620cb5973f9a77233a700b06612462678e5.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" selected="selected">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast">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>