Vaadin 7.5.4: CustomFieldSerializers not considered during compilation

We are facing a strange problem during compilation when we want to send a custom bean `TestBean` from server to client in Vaadin 7.5.4 using `ClientRpc`.

    public class TestBean implements Serializable {
    
        private TestDto dto;

        public TestDto getDto() {
            return dto;
        }

        public void setDto(TestDto dto) {
            this.dto = dto;
        }
    }

    public class TestDto implements Serializable {
    
        private String message;
    
        public TestDto(String message) {
            this.message = message;
        }

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this.message = message;
        }

    }

During compliation we get the following error:
    
    [ERROR] Rebind result 'my.test.TestDto' has no default (zero argument) constructors

Because `TestDto` does not have a default (zero argument) constructor, we have implemented a `CustomFieldSerializer` and placed it in the same package of `TestDto`. Unfortunately, our custom serializer seems not to be considered by the vaadin compiler.

    public final class TestDto_CustomFieldSerializer extends CustomFieldSerializer<TestDto> {

        public static void deserialize(SerializationStreamReader streamReader, TestDto instance) {
            // No fields
        }

        public static TestDto instantiate(SerializationStreamReader streamReader) throws SerializationException {
            return new TestDto(streamReader.readString());
        }

        public static void serialize(SerializationStreamWriter streamWriter, TestDto instance) throws SerializationException {
            streamWriter.writeString(instance.getMessage());
        }

        @Override
        public void deserializeInstance(SerializationStreamReader streamReader, TestDto instance) throws SerializationException {
            deserialize(streamReader, instance);
        }

        @Override
        public boolean hasCustomInstantiateInstance() {
            return true;
        }

        @Override
        public TestDto instantiateInstance(SerializationStreamReader streamReader) throws SerializationException {
            return instantiate(streamReader);
        }

        @Override
        public void serializeInstance(SerializationStreamWriter streamWriter, TestDto instance) throws SerializationException {
            serialize(streamWriter, instance);
        }
    
    }

We have also found out that all built-in `CustomFieldSerializer` are working fine, but compilation always fails, when we use custom implementations and place them in the corresponding packages. In a separate test case, we have tried to send a collection `HashBasedTable ` of `guava-gwt` from client to server. This class is also missing a default (zero argument) constructor, but the `CustomFieldSerializer` implementation `HashBasedTable_CustomFieldSerializer` is provided in the same package. During compilation, we get the same error:

    [ERROR] Rebind result 'com.google.common.collect.HashBasedTable' has no default (zero argument) constructors.

Refering to the GWT documentation, this seems to be a proper solution, when classes are missing a default (zero argument) constructor:
http://www.gwtproject.org/doc/latest/DevGuideServerCommunication.html#DevGuideCustomSerialization

Has anybody an idea what we are making wrong?