No PropertyTypeExtractor available for type void in CompositeUserType

Hi,

I'm trying to update from hibernate 5.2.18 to 5.4.4 and I'm facing a regression with a type in CompositeUserType that hibernate can't handle.

To simplify my problem, I have the following “Population”entity, containing a non entity “Matrix” object:

And the following xml mapping:

“Matrix” object can be resumed as:

Since, update, hibernate complains about a strange type into 'Matrix' object : java.util.List<?>[]
It's ok, that hibernate can't handle that, but why does hibernate throw the following error for a field inside a CompositeUserType ?