When the java.jnlp module is built a modular jar is constructed from the class files. The boot JDK 9 jar tool is used to construct the modular jar.

For class file versions > 53 the use of the boot JDK 9 jar tool will result in a build failure. This is because the boot JDK 9 jar tool attempts to process the module-info.class file and fails because the class file version is not 53.

The build infrastructure could be modified to use the built jar tool.