Index: /applications/editors/josm/plugins/build-common.xml
===================================================================
--- /applications/editors/josm/plugins/build-common.xml	(revision 34366)
+++ /applications/editors/josm/plugins/build-common.xml	(revision 34367)
@@ -102,4 +102,6 @@
                 <pathelement location="${error_prone_ant.jar}"/>
             </compilerclasspath>
+            <compilerarg value="--add-modules" if:set="isJava9" unless:set="isJava11" />
+            <compilerarg value="java.activation,java.se.ee" if:set="isJava9" unless:set="isJava11" />
             <compilerarg value="-Xlint:deprecation"/>
             <compilerarg value="-Xlint:unchecked"/>
@@ -529,4 +531,6 @@
                     <path refid="test.classpath"/>
                 </classpath>
+                <compilerarg value="--add-modules" if:set="isJava9" unless:set="isJava11" />
+                <compilerarg value="java.activation,java.se.ee" if:set="isJava9" unless:set="isJava11" />
 				<compilerarg value="-Xlint:all"/>
 				<compilerarg value="-Xlint:-serial"/>
@@ -542,4 +546,6 @@
                 <junit printsummary="yes" fork="true" forkmode="once" dir="${basedir}">
                     <jvmarg value="-Dfile.encoding=UTF-8"/>
+                    <jvmarg value="--add-modules" if:set="isJava9" unless:set="isJava11" />
+                    <jvmarg value="java.activation,java.se.ee" if:set="isJava9" unless:set="isJava11" />
                     <jvmarg value="--add-opens" if:set="isJava9" />
                     <jvmarg value="java.base/java.lang.reflect=ALL-UNNAMED" if:set="isJava9" />