PHP Error: require(./index.phptools/support/database_cleaner.php): failed to open stream: No such fi

PHPBB ERROR:
[phpBB Debug] PHP Notice: in file /stk/tools/support/mysql_upgrader.php on line 48: require(./index.phptools/support/database_cleaner.php): failed to open stream: No such file or directory

This occurs on 6 different instances where I've downloaded new STK ZIPs, and it occurs on all the httpds i've run (Apache and lighttpd, as well as nginx).

Does this file truly exist in the stk folder, or is this a bug specific to my install?