tapestry5 - @SessionState - ClassCastException

I've created a simple enum and used it as a session state object but after few calls to that object tapestry was throwing me a ClassCastException, sth like:
my.project.pages.MyEnum cannot be cast to my.project.pages.MyEnum

I was trying to create POJO and put my new enum inside but it didn't help.

Finally it turns out that it was because my enum was inside pages package (http://tapestry.formos.com/nightly/tapestry5/faq/general.html#classcastexception). After moving my new enum to different package everything seemed to work correctly