Validation Check Failure, what step am I missing? meta@dtb:uid content 'null' should conform to unique-identifier in content.opf

[Michael Joyner]

Hello all,

1st, Thanks for such an easy to use, SENSIBLE library.

2nd, I am getting a validation error after assigned an ISBN to an epub:

meta@dtb:uid content 'null' should conform to unique-identifier in content.opf

This is the code fragment I am using to do the assignment with:

Identifier isbn = new Identifier(Identifier.Scheme.ISBN, isbnFormatted);
        isbn.setBookId(true);
meta.addIdentifier(isbn);

What am I not doing right?