I've reduced my problem to a very simple maven project, located here as zip-file: /https://www.file-upload.net/download-13793489/deeschd.zip.html/ doing a /mvn test/ runs fine with Java-11. uncommenting /// requires transitive ch.qos.logback.classic;/ in /src/main/jave/module-info.java/ and running /mvn test/ again leads to an NPE. Why does the mentioning of an existing module in /module-info.java /lead to an NPE? // This source code is a reduction of an existing project. It has been has been moved from Java-8 to Java-11. The source code contains a /LogbackConfigurator.java/ (implementing ch.qos.logback.classic.spi.Configurator). /LogbackConfigurator.java/ needs /ch.qos.logback.classic/ in /module-info.java/ in order to compile. Am I doing something wrong, or is this a bug? Any help welcome Rolf