Index: /trunk/build.xml
===================================================================
--- /trunk/build.xml	(revision 13490)
+++ /trunk/build.xml	(revision 13491)
@@ -377,4 +377,5 @@
             <doctitle><![CDATA[<h2>JOSM - Javadoc</h2>]]></doctitle>
             <bottom><![CDATA[<a href="https://josm.openstreetmap.de/">JOSM</a>]]></bottom>
+            <arg value="-html4" if:set="isJava9" />
             <arg value="--add-exports" if:set="isJava9" />
             <arg value="java.base/sun.security.util=ALL-UNNAMED" if:set="isJava9" />