Unzipping a large Moodle 2.3 course backup archive (as part of the restore process) in Moodle 2.3.2 (build 20120927) times out every time (> 30 sec) and it isn't clear how to increase this threshold:

PHP Fatal error: Maximum execution time of 30 seconds exceeded in lib/filestorage/zip_packer.php on line 268

It is worth noting that packing the archive works fine; courses are backed up nightly. It's only the unpacking which is timing out.