Wildcard/underscore serialization issue Mapping Exception

[ktruong5]

I have a case class with Option[Map[_, _]] and it is working with tests passing with Scala 2.13.4. I have upgraded to any Scala version 2.13.X (after 2.13.6) and it fails with the following error.

org.json4s.package$MappingException: Unexpected type info ExistentialType()

I have also changed the Map[Any, Any] and Map[String, String] and my test passes.

What is the reason for this behavior?

org.json4s version 3.5.5 and 3.6.12

Scala version 2.13.4 and versions greater than 2.13.6