Liquibase - NVarcharType on Derby Fails

Derby does not have support for NVarchar. Currently the execution of NVarchar against Derby fails with "Caused by: ERROR 0A000: Feature not implemented: NATIONAL CHAR VARYING".

It could be worked around by adding Derby to NVarcharType#toDatabaseDataType. I am trying with 3.0.2 and the plugins seems to have changed. How do I write and extension to work around this issue?

public class NVarcharType extends CharType {

    @Override

    public DatabaseDataType toDatabaseDataType(Database database) {

        if (database instanceof HsqlDatabase || database instanceof PostgresDatabase 

            return new DatabaseDataType("VARCHAR", getParameters());

        }

Regards,

Rahul