django - Why is the Prefetch object being ignored in prefetch_related? -

using django 1.7:

my queryset looks this:

    return super(employeeviewset, self).get_queryset()\            .filter(status__deleted_flag=false, **filter_kwargs)\            .prefetch_related('phone_number_set', 'email_address_set', 'street_address_set',                              prefetch('file_set', employeefile.objects.active().select_related('content_type')))\            .order_by('last_name', 'first_name') 

djdt shows prefetch query executed

select ••• "employees_employeefile" inner join "employees_employeefiletype"  on ("employees_employeefile"."content_type_id" = "employees_employeefiletype"."id" ) ("employees_employeefile"."deleted_at" null         , "employees_employeefile"."owner_id" in (53, 81, ...))  order "employees_employeefile"."created_at" desc 

then djdt shows each employee getting requeried same list of files

select ••• "employees_employeefile"  ("employees_employeefile"."owner_id" = 53         , "employees_employeefile"."deleted_at" null)  order "employees_employeefile"."created_at" desc 

they queries same me, , modelmanager method being used select same 1 (employeefile.objects.active()) vs employee.file_set.active()

also, tried removing select_related('content_type') in case problem