You need to enable <module>mod_logio</module> to use this.</td></tr>
<tr><td><code>%O</code></td>
- <td>Bytes sent, including headers. Cannot be zero. You need to
- enable <module>mod_logio</module> to use this.</td></tr>
+ <td>Bytes sent, including headers. May be zero in rare cases
+ such as when a request is aborted before a response is sent.
+ You need to enable <module>mod_logio</module> to use this.</td></tr>
<tr><td><code>%S</code></td>
<td>Bytes transferred (received and sent), including request and headers,