Java flag to enable extended Serialization debugging info

I am currently struggling with HTTP Session replication on tomcat with complex objects.

Some objects implement Serializable but hold non-serializable members.

Un开发者_开发知识库fortunately, the stacktraces do not provide much useful info here by default.

there is a flag -XX:???? to enable verbose class names in the stacktrace when a NotSerializableException occurrs. this flag would help me a lot finding the source of the error. but i forgot its name

What is the name of the flag?

-Dsun.io.serialization.extendedDebugInfo=true