Reading the blog on the 5.0.0 release http://in.relation.to/2015/08/20/hibernate-orm-500-final-release/ section "Attribute Converter support" where it is pointed out that converters are now called for null-values I have hoped that this issue could be closed. I thought this to be a bug because it is neither documented behaviour nor what you expect after you register a UserType which acts upon null-values. It is not even consistent with persistance of issues rendering it impossible to use the Criteria Api to update certain fields like you could update them on a materialized entity. Of course the implementation does this deliberately and it may be bad style to switch null for something else, but I guess this sort of half-backed support isn't helping either.