[CentOS] rpm building and hyphens in Version tags

According to http://www.rpm.org/api/4.4.2.2/specfile.html a
Version: tag can contain a hyphen, as the tarball for the source
I am compiling is named 2.3-pre4 etc.

When I try to build it I get an error about the illegal char?

Anyone know about the discrepancy between the docs and RHEL's
rpmbuild? Without recreating a new tarball and bungling the name
how does one gracefully handle this?

Thanks!
jlc