Consider collection \"fruits\", in which I have this document (I\'m using Python\'s pymongo driver, btw):
{
\'_id\' : \'lemons\',
\'weight\'
Have you tried adding another inclusion projection? I think you may be able to add something trivial like foo:1 (that is not a real field) and it should work.
Like so:
{ 'countries' : { '$slice' : [0, 3] }, '_id' : 0, foo : 1 }
If it doesn't work I suggest filing a bug with mongo. They are actually very good about responding to bugs.