NEST - Don't index certain values with bulk requests

I have a class that represents the data I want to store in ES that contains mostly integers. However, I don't want to index fields which are a particular value (in this case, 0). I'm trying to get the API to completely disregard fields that are 0 so they don't get indexed.

Currently I'm doing this, but it doesn't work (the zeroes are indexed anyway):

class ElasticDataRepresentation
        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        [Nest.Number(Name = "postid", NullValue = 0)]
        public uint PostID { get; set; }

        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        [Nest.Number(Name = "datapointid", NullValue = 0)]
        public int DataPointID { get; set; }

and then run the indexing in bulk with the following code. Everything works as expected except that I can't get it to disregard the zeroes:

var descriptor = new Nest.BulkDescriptor();
foreach (var pi in items)
    //Construct the ID
    string id = pi.DataPointID.ToString() + "_" + pi.PostID;
    //Add this document to the bulk request
    descriptor.Index<ElasticDataRepresentation>(op => op.Document(pi).Id(id).Index(Model.ElasticSearchIndexName).Type(Model.ElasticSearchTypeName));


//Execute the bulk index request
var result = client.Bulk(descriptor);

Any ideas how this can be resolved? Thanks!