Thanks for finding the cause quickly ! yes, the problem goes away after make the test classes in a named package. The small web app was from a casual dev test and works with Java 8+weld. Unnamed package classes are allowed, in this situation, by Java language specification. This appears to be a limitation in Weld+Tomcat+Java9 since a similar test works in Weld3.0.0.Beta1 +Java 9 SE environment.