Error: Attempted to serialize java.lang.Class: Forgot to register a type adapter?

Hi,

 I am using SOAP UI version 5.3.0. I have been using the tool for my application testing. Recently we upgraded the Spring version of application from 4.2.1 to 4.2.6 and after which we started getting below the error while executing test suite.

Error: Attempted to serialize java.lang.Class: <application class name> Forgot to register a type adapter?.

Can you please let me know how to fix this issue?

Regards

SN