Elasticsearch Binary subaggregations

AggregationBuilder.java

// If I change toXContent from AggregationBuilder.java, it produces a correct output

@Override
public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
    builder.startObject(getName());

    builder.field(type);
    internalXContent(builder, params);

    if (aggregations != null || aggregationsBinary != null) {

        if (aggregations != null) {
            builder.startObject("aggregations");
            for (AbstractAggregationBuilder subAgg : aggregations) {
                subAgg.toXContent(builder, params);
            }
            builder.endObject();
        }

        else {
            if (XContentFactory.xContentType(aggregationsBinary) == builder.contentType()) {
                builder.rawField("aggregations", aggregationsBinary);
            } else {
                builder.field("aggregations_binary", aggregationsBinary);
            }
        }

    }

    return builder.endObject();
}

gistfile1.java

import org.elasticsearch.common.xcontent.ToXContent;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentHelper;
import org.elasticsearch.common.xcontent.json.JsonXContent;
import org.elasticsearch.search.aggregations.AggregationBuilders;
import org.elasticsearch.search.aggregations.bucket.terms.TermsBuilder;
import java.io.IOException;

public class TestSubAggregation {

    public static void main(String[] args) throws IOException {
        // Build a simple term aggregation

        TermsBuilder termsBuilder = AggregationBuilders.terms("test").field("testfield");

        // Build a simple term sub aggregation
        TermsBuilder subTerm = AggregationBuilders.terms("subtest").field("subtestfield");

        // Add sub aggregation as an AggregationBuilder
        termsBuilder.subAggregation(subTerm);
        // It produces a correct output
        System.out.println(XContentHelper.toString(termsBuilder));

        // Reset term aggregation
        termsBuilder = AggregationBuilders.terms("test").field("testfield");

        // Create an XContentBuilder from sub aggregation
        XContentBuilder subTermContentBuilder = JsonXContent.contentBuilder().startObject();
        subTerm.toXContent(subTermContentBuilder, ToXContent.EMPTY_PARAMS);
        subTermContentBuilder.endObject();

        // Add sub aggregation as a XContentBuilder (binary_aggregation)
        termsBuilder.subAggregation(subTermContentBuilder);

        // Produces an incorrect output (two aggregations levels instead of one)
        System.out.println(XContentHelper.toString(termsBuilder));

    }
}