GlassFish 4 NoClassDefFoundError javax/servlet/Filter JAMon

I'm using GlassFish 4.0. I have a Java Class Library application which contains a Java class which implements javax.servlet.Filter and uses JAMon's Monitor. The Library application uses jamon-2.7.jar as a library. I also have an EAR which contains an EJB application and a WAR application. The WAR application uses the Java Class Library application as a library. I have jamon-2.7.jar in GF's glassfish-4.0/glassfish/domains/domain1/lib/ext directory. I can build all apps fine, but when I deploy the EAR to GF4 using NetBeans 7.4, I get the following error:

WebModule[/myapp-war]Exception starting filter jamonFilter
java.lang.NoClassDefFoundError: javax/servlet/Filter

Any ideas as to why this is happening?