Upserts with $in clause results in either the operator being added to the document or it being ignored depending on nesting depth :

> db.test.update({a:{$in:[1]}}, {$set:{v:1}}, true, false)
> db.test.find()

{ "_id" : ObjectId("4ecd047da0627e0c2e464b5e"), "v" : 1 }

> db.test.update({a:{b:{$in:[1]}}}, {$set:{v:1}}, true, false)
> db.test.find()
{ "_id" : ObjectId("4ecd0487a0627e0c2e464b5f"), "a" : { "b" :

{ "$in" : [ 1 ] }

}, "v" : 1 }

Is this intended? And if not which one is the correct behaviour?