[Forum] Ajax edit, "Call to undefined function fetch_max_upload_size()"

[high]

When the ajax edit is used it returns this

Url:

http://codexplosion.com/ajax.php?do=quickedit&p=33121

Resp:

<br />
<b>Fatal error</b>:  Call to undefined function fetch_max_upload_size() in <b>/includes/functions_attach.php</b> on line <b>20</b><br />

functions_file.php is upload and does contain that function. What would be another reason for this? I noticed ajax.php doesn't contain a reference to "functions_file.php".

Edit:

Adding

        require_once(DIR . '/includes/functions_file.php');

on line 474 in ajax.php fixed the error.

But why my forum is having this problem and not others is puzzling me.