Serialization of Scala Enum with Casbah

How to serialize a Scala enum using Casbah?

I have this error:

[info]   java.lang.IllegalArgumentException: can't serialize class scala.Enumeration$Val
[info]   at org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:270)
[info]   at org.bson.BasicBSONEncoder.putIterable(BasicBSONEncoder.java:295)