[web2py] Puzzle: reference table not working?

[lyn2py]

I created a brand new app for this.

Code:
db.define_table('location', 
    Field('city', 'string',length=255,requires=IS_NOT_EMPTY()),
    Field('state', 'string',length=255,requires=IS_NOT_EMPTY()),
    Field('country', 'string',length=255,requires=IS_NOT_EMPTY()),
)
db.define_table('person', 
    Field('name','string',length=255,requires=IS_NOT_EMPTY()),
    Field('location_id','reference location',default=location.id),
)

And the error that comes up is:
<type 'exceptions.NameError'> name 'location' is not defined

Traceback (most recent call last):
  File "/Users/xxx/web2py/source/gluon/restricted.py", line 205, in restricted
    exec ccode in environment
  File "/Users/xxx/web2py/applications/newapp/models/main.py" 
<http://127.0.0.1:8000/admin/edit/babybook/models/main.py>, line 40, in <module>
    Field('location_id','reference location',default=location.id),
NameError: name 'location' is not defined

Funny thing is, the exact same code ("reference <some_table>") is working on 
other apps, but why not this new app?

Thanks.

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