[web2py] SQLFORM -> IS_UPLOAD_FILENAME question.

[rdodev]

I have a table definition as follows:

db.define_table('UPLOAD',
    Field('custom_name',type='string', required=True, length=40),
    Field('file_name',  type='upload', required=True, 
requires=IS_UPLOAD_FILENAME(extension='zip|cro')),
)

from which I'm generating a SQLFORM from. When I get the POST request, the 
db insert doesn't fail or throws any errors even with files that are 
neither .zip nor .cro. 

Any help would be much appreciated.