lektor checkboxes `[u'` ouput error?

my first attemp in lektor: I want to create my own Data Model for architectural works record. I have a wierd ouput for checkboxes and lists like:

    [u'corporate & commercial', u'interiors']

Where the poject.ini is

[fields.type]
label = Project type
type = checkboxes
choices = corporate & commercial, residential, interiors, public,hotel/tourism, university, art gallery, restoration, spa, auditorium,  installations, landscape
choice_labels = corporate & commercial, residential, interiors, public, hotel/tourism, university, art gallery, restoration, spa, auditorium,  installations, landscape

and the project.html has:

Where are those [u' in the ouput coming from? What am I missing?

Thank you

AR (running lektor 3.0.1 on win 7/64)