Hello. It seems that LoggerFactory misbehaves when used from a modular project: I have a very simple repro case here: https://github.com/io7m/logback-bug-20180209 The error is: Exception in thread "main" java.util.ServiceConfigurationError: ch.qos.logback.classic.spi.Configurator: module ch.qos.logback.classic does not declare `uses` at java.base/java.util.ServiceLoader.fail(ServiceLoader.java:588) at java.base/java.util.ServiceLoader.checkCaller(ServiceLoader.java:574) at java.base/java.util.ServiceLoader.<init>(ServiceLoader.java:503) at java.base/java.util.ServiceLoader.load(ServiceLoader.java:1639) at ch.qos.logback.classic/ch.qos.logback.classic.util.EnvUtil.loadFromServiceLoader(EnvUtil.java:48) at ch.qos.logback.classic/ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:155) at ch.qos.logback.classic/ch.qos.logback.classic.spi.LogbackServiceProvider.initializeLoggerContext(LogbackServiceProvider.java:49) at ch.qos.logback.classic/ch.qos.logback.classic.spi.LogbackServiceProvider.initialize(LogbackServiceProvider.java:40) at org.slf4j/org.slf4j.LoggerFactory.bind(LoggerFactory.java:153) at org.slf4j/org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:141) at org.slf4j/org.slf4j.LoggerFactory.getProvider(LoggerFactory.java:419) at org.slf4j/org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:405) at org.slf4j/org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:354) at org.slf4j/org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:380) at com.io7m.bugs.logback/com.io7m.bugs.logback.Main.<clinit>(Main.java:8) The code simply calls: private static final Logger LOG = LoggerFactory.getLogger(Main.class); ... with a module descriptor: module com.io7m.bugs.logback { requires org.slf4j; } -- Mark Raynsford | http://www.io7m.com