# [Tex/LaTex] Invalid ISBN in value of field ‘isbn’ (-1)

biberbiblatexwarnings

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:

@book{unep2016,
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}
}


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.