Ok, so the impl of org.jboss.weld.util.Beans.removeDisabledBeans(Set<T>, BeanManagerImpl) is different in 2.x and 3.x. It should be safe to align the 3.x impl with 2.x. However, I don't think creating 1000 set copies should make such a difference... unless the sets are really huge. Thomas Wöckinger What are the results of your test with 2000 classes?