It appears that if you have a module with a dependency on org.jboss.modules it is no longer possible to use getResource() to get the class file:

loader.getResource("org/jboss/modules/Module.class") = null
loader.loadClass("org.jboss.modules.Module") =

"class org.jboss.modules.Module"

This breaks some java agents, as it can be necessary to get access to these classes to recompute the stack map table attribute.