rmic accesses the class files of classes on the boot class path. It uses the value of the sun.boot.class.path property and assumes the elements zip files or directories with class files. This doesn't work with a modular image where the classes are stored in jimage format. This code will need to be updated to work with modular image. One approach is to use the NIO "jimage" file system provider in the same way that javac uses it.