When running Elytron subsystem tests the following warnings are displayed on system console on jDK11:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.wildfly.extension.elytron.SSLDefinitions (file:/home/opalka/git/redhat/PUBLIC/wildfly-core/elytron/target/classes/) to method com.sun.net.ssl.internal.ssl.Provider.isFIPS()
WARNING: Please consider reporting this to the maintainers of org.wildfly.extension.elytron.SSLDefinitions
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

It is possible to turn off this warning by setting appropriate JDK11 --add-opens parameter.