Okay, I changed that.
(BTW why do you restrict yourselves to valid ISBNs? There are books with invalid ISBNs ( http://en.wikipedia.org/wiki/International_Standard_Book_Number#Errors_in_usage ) but cleanISBN ( https://github.com/zotero/zotero/blob/master/chrome/content/zotero/xpcom/utilities.js#L280 ) would in these cases return false.)