AvroTypeException thrown with version change on optional record

[Francois Forster]

Hi,
I'm trying to test versioning in Avro data serialization and I'm seeing an 
AvroTypeException thrown when I add a new field to an optional record.
Here's the V1 schema:
@namespace("v1")
protocol Service {
     record Result {
         string id;
         string text;
         boolean isRecommended;
     }

     record Response {
         int version;
         boolean success;
         union {null, Result} results;
     }
}
V2 (added isFeatured to Result):
@namespace("v2")
protocol Service {
     record Result {
         string id;
         string text;
         boolean isRecommended;
         boolean isFeatured;
     }

     record Response {
         int version;
         boolean success;
         union {null, Result} results;
     }
}
Here's the code:

import org.apache.avro.Protocol;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.avro.specific.SpecificDatumWriter;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;

public class AvroServiceMain {

    public static void main(String[] args)
            throws Exception {
        Protocol protocol_v2 = Protocol.parse(new File("TestCase_v2.avdr"));
        Protocol protocol_v1 = Protocol.parse(new File("TestCase_v1.avdr"));
        SpecificDatumWriter< v2.Response>  responseSerializer = new 
SpecificDatumWriter< v2.Response>(protocol_v2.getType("Response"));
        SpecificDatumReader< v1.Response> responseDeserializer = new 
SpecificDatumReader< 
v1.Response>(protocol_v2.getType("Response"),protocol_v1.getType("Response"));

        v2.Response responseV2 = new v2.Response();
        responseV2.setVersion(2);
        responseV2.setSuccess(true);
        v2.Result result = new v2.Result();
        result.setId("1234");
        result.setIsRecommended(false);
        result.setIsFeatured(true);
        result.setText("Some text...");
        responseV2.setResults(result);

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        BinaryEncoder encoder = EncoderFactory.get().directBinaryEncoder(baos, 
null);

        responseSerializer.write(responseV2, encoder);
        byte[] bytes = baos.toByteArray();
        ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
        BinaryDecoder decoder = DecoderFactory.get().directBinaryDecoder(bais, 
null);

        v1.Response responseV1 = new v1.Response();
        responseDeserializer.read(responseV1, decoder);

        System.out.println(responseV1);

    }

}

Here's the exception thrown:
Exception in thread "main" org.apache.avro.AvroTypeException: Found {
  "type" : "record",
  "name" : "Result",
  "namespace" : "v2",
  "fields" : [ {
    "name" : "id",
    "type" : "string"
  }, {
    "name" : "text",
    "type" : "string"
  }, {
    "name" : "isRecommended",
    "type" : "boolean"
  }, {
    "name" : "isFeatured",
    "type" : "boolean"
  } ]
}, expecting [ "null", {
  "type" : "record",
  "name" : "Result",
  "namespace" : "v1",
  "fields" : [ {
    "name" : "id",
    "type" : "string"
  }, {
    "name" : "text",
    "type" : "string"
  }, {
    "name" : "isRecommended",
    "type" : "boolean"
  } ]
} ]
      at org.apache.avro.io.ResolvingDecoder.doAction(ResolvingDecoder.java:231)
      at org.apache.avro.io.parsing.Parser.advance(Parser.java:88)
      at 
org.apache.avro.io.ResolvingDecoder.readIndex(ResolvingDecoder.java:206)
      at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:148)
      at 
org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:173)
      at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:144)
      at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:135)
      at TestCaseMain.main(TestCaseMain.java:44)


The exception doesn't occur when the field is not Optional.

Am I missing something or does this look like a bug?

Thanks,

Francois.