The AvailableRealmsCallback should not result in a NPE if there is no mechanism configuration. ---------------------------------------------------------------------------------------------- Key: ELY-1745 URL: https://issues.redhat.com/browse/ELY-1745 Project: WildFly Elytron Issue Type: Bug Components: API / SPI Reporter: Darran Lofthouse Priority: Major Fix For: 1.11.0.CR5 The NPE is due to the following code: - {noformat} } else if (callback instanceof AvailableRealmsCallback) { Collection<String> names = stateRef.get().getMechanismConfiguration().getMechanismRealmNames(); if (log.isTraceEnabled()) { log.tracef("Handling AvailableRealmsCallback: realms = [%s]", String.join(", ", names)); } if (! names.isEmpty()) { ((AvailableRealmsCallback) callback).setRealmNames(names.toArray(new String[names.size()])); } handleOne(callbacks, idx + 1); {noformat} If mechanism configuration is mandatory this should report an appropriate error, if not it should fallback to specifying an empty list.