Goodreads Librarians Group discussion

Hello,

I just added a new edition of a book, but the ISBN converter page told me the number 9731580904 is invalid and that the check digit should be 5. I changed the last number from 4 to 5 and it worked. Is it possible that the publisher/printing company did a mistake back then?

I searched everywhere the new/modified ISBN, but it didn't give me any results - but the old one has only 2 matches on Google, so whatever.

Is this allowed? I have the physical book in my hand, I can prove that it exists and the ISBN I entered is also correct, see the links below:
https://moly.hu/kiadasok/1219 and
https://rmk90.adatbank.ro/print.php?k...

Please confirm if I proceeded correctly. Thank you!

It could be a printing error, but we can't know what the error was. It is not necessarily the last digit, it could have been a digit in the middle (Which in the correct version would have led to this check digit). So you should not just change the check digit.