Travis build is for master currently errors-out due to problems with toolchain: [INFO] Required toolchain: jdk [ version='1.6' ] [ERROR] No toolchain found for type jdk [ERROR] Cannot find matching toolchain definitions for the following toolchain types: jdk [ version='1.6' ] [INFO] ------------------------------------------------------------------------ [INFO] Reactor Summary: [INFO] [INFO] SLF4J .............................................. FAILURE [ 3.279 s] [INFO] SLF4J API Module ................................... SKIPPED The build also requires JDK9 to complete in Travis.  A matrix build is probably indicated, but let's get it building OK first. This is fixed by https://github.com/qos-ch/slf4j/pull/187  . Last failed master Travis: [https://travis-ci.org/qos-ch/slf4j/builds/317439667 S|https://travis-ci.org/qos-ch/slf4j/builds/317439667]uccess from PR: https://travis-ci.org/qos-ch/slf4j/builds/300534125 Please review and consider merging.