Script Filters referencing a field with special characters

Hi all,
I have a Script Filters defined in the couchdb river.
In this script I need to refer to a field of the documents which has special characters on it, e.g. '-'
So the field would be, for example: 'number-of-houses'

How can I refer to this field from the Script Filter ??

In a normal javascript in a view I would use doc['number-of-houses'], but in the Script Filters I don't know...
I tried:


...but none of these options works.