Same here: I get this error with 5.0.0.Beta2 and it worked with 4.3.8.
As I stated in HHH-8854 and HHH-8958 dealing with java reflection is painful. Use a proper highlevel library for that to avoid such ugly bugs. If you do not want to depend on third party create your own but be warned that this is a lot of effort and you might want to more or less copy from mmm or guava.