When the following annotation is present on an enum type entity field:
Queries using JPQL IN expressions on this field won't work correctly anymore. This issue has been described in forum post 1254 (JPA JPQL WHERE clause for IN :variable not working if variable is a list of Enums).
See also the attached test case (play with adding and removing the Enumerated annotation).
Best regards, and thank you for this great piece of work!