4gb Limit

Just tried to use piguybuilder and it failed at the end saying that the image was too large.

With ISO level 3, no restrictions (other than ISO-9660:198 apply. Starting
with this level, genisoimage also allows files to be larger than 4 GB by
implementing ISO-9660 multi-extent files.

So genisomage supports > 4GB images using iso level 3 so why fail the build?

Thanks
Dave