MultiClassesQueryLoader.executeLoad fastpaths the N=1 case via load(), whilst the N>1 case goes via objectInitializer.initializeObjects. As a result the actual objects are returned for the multiple result case, but a proxied unpopulated object (but with populated JavassistLazyInitializer handler) is returned in the single result case. All fields are affected, not just the id field. 5.5.4.Final (i.e. the current wildfly-warm release) release is also impacted by this.