Using OrientDB's JDBC driver with ActiveRecord

What is the proper way of using OrientDB's JDBC driver with ActiveRecord?

I am trying to connect a Rails 3.2 application to OrientDB 1.4. I installed the gem activerecord-jdbc-adapter, and configured the database.yml as follows:

development:
  adapter: jdbc
  username: admin
  password: admin
  driver:   com.orientechnologies.orient.jdbc.OrientJdbcDriver
  url:      jdbc:orient:local:db/test_db2

I load the OrientDB's JDBC driver as follows:

# in config/application.rb:
require '/home/myuser/jars/orientdb-jdbc-1.4.0-all.jar'

The following exception is being thrown when the application starts (using rails s):

java.lang.NullPointerException
    at arjdbc.jdbc.RubyJdbcConnection.unmarshalResult(RubyJdbcConnection.java:1187)
    at arjdbc.jdbc.RubyJdbcConnection.set_native_database_types(RubyJdbcConnection.java:537)
    at arjdbc.jdbc.RubyJdbcConnection$INVOKER$i$0$0$set_native_database_types.call(RubyJdbcConnection$INVOKER$i$0$0$set_native_database_types.gen)
    ...

Is there something missing in my configuration? What is the proper way of using OrientDB's JDBC driver with ActiveRecord?