I have a little problem with biber. When I run it with --validate_datamodel, it warns me

WARN - Datamodel: Entry 'unep2016' (mybibfile.bib): Invalid ISBN in value of field 'isbn' (-1)

As "it does not matter if you use the 13 or 10 digit format" (Guido), the warning must come from somewhere else. I have tried the ISBN as 9789280735806 and with hyphens in different places, e.g. 978-9280-7358-06. Here's the bib entry:

location = {Nairobi},
author = {UNEP},
publisher = {United Nations Environment Programme},
isbn = {9789280735806},
title = {{Marine Plastic debris and microplastics - Global lessons and research to inspire action and guide policy change}},
year = {2016}
  • 1
    isbn-check.de/… says that 9789280735806 is not a correct ISBN, so does formvalidation.io/validators/isbn
    – moewe
    Oct 8, 2017 at 20:15
  • 2
    That ISBN is invalid; the final digit should be 2, according to hahnlibrary.net/libraries/isbncalc.html and, indeed, if I input 9789280735802 in isbn-check.com, I get a pointer to that book.
    – egreg
    Oct 8, 2017 at 20:19
  • The world of TeX will never stop to amaze me. Biber checks for validity in ISBNs!? Who had the idea to implement ISBN validation. This just blows all my minds!
    – thymaro
    Oct 8, 2017 at 20:20
  • Just downloaded a copy of the report and the copyright page indeed indicates 978-92-807-3580-6, but the final digit should be a 2 to pass vlaidation.
    – moewe
    Oct 8, 2017 at 20:21
  • 2
    I know, right!? Those bastards at UNEP can't even get the ISBN of their own publication right! :D
    – thymaro
    Oct 8, 2017 at 20:24

1 Answer 1


Biber does not only check the datamodel integrity, it also explicitly checks ISBNs for validity when in --validate_datamodel mode. As it turns out 978-92-807-3580-6 (9789280735806) as indicated on the report's copyright page is not a valid ISBN Most likely the last digit (the check digit) should be a 2 instead.

ISBN validation was implemented following discussions in Automatically validate and format ISBNs. With --isbn-normalise you can get hyphens in the right place even if they are missing in the .bib file. --isbn13 forces 13-digit ISBNs, --isbn10 the old 10-digit format.

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