The constructor of MappedConstructor accesses the PersistentEntity constructor unguarded to iterate over it's parameters. This results in a NullPointerException. Generally instantiating a MappedConstructor with a PersistentEntity not owning a PersistenceConstructor is invalid as this essentially means we have an ambiguity in constructors (multiple constructors taking arguments without one explicitly selected through @PersistenceConstructor. This indicates the class currently inspected actually either needs to be mapped correctly or a custom converter applied when reading. Thus we should reject the PersistentEntity throwing a MappingException indicating potential ways to solve the problem.