weld-servlet.jar contains slf4j version > 1.5.10. SLF4J is currently in 1.6.X series and has an incompatibility with 1.5.X. weld-servlet should not contain slf4j 1.5.X This creates some nasty problems with projects depending on SLF4J 1.6. It has been a show stopper for me and using JBoss AS 7 or Glassfish is not an option unfortunately. weld-servlet-int pom is old and has not the 1.1.4.Final version.