This is related to MONGOID-1293

When I try to remove attribute in embedded document following query is executed:

update(

{"_id"=>BSON::ObjectId('4f71b5d2289ffe2840000001')}

, {"$set"=>

{"embedded_doc.my_attribute"=>nil}

, "$unset"=>{"embedded_doc.my_attribute"=>true}})

It ends up with attribute still present in document and being nil.