Does the AttributeConverter really make any difference? If you were not using an AttributeConverter would the exception go away?

A test case would be great...

I think Hardy Ferentschik may be right. This does seem to duplicate HHH-6475, but its hard to say as neither supplies a test case. Hardy Ferentschik did work out a PR that supposedly fixes HHH-6475. Has anyone tried that in regards to the problem being reported here?