--- old/make/gendata/GendataHtml32dtd.gmk	2020-03-23 19:56:26.875962774 +0100
+++ new/make/gendata/GendataHtml32dtd.gmk	2020-03-23 19:56:26.555962776 +0100
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2020, Oracle and/or its affiliates. All rights reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -23,6 +23,10 @@
 # questions.
 #
 
+TOOL_DTDBUILDER = $(JAVA_SMALL) -Ddtd_home=$(TOPDIR)/make/data/dtdbuilder \
+    -Djava.awt.headless=true \
+    -cp $(BUILDTOOLS_OUTPUTDIR)/jdk_tools_classes org.openjdk.buildtools.dtdbuilder.DTDBuilder
+
 GENDATA_HTML32DTD :=
 
 HTML32DTD = $(JDK_OUTPUTDIR)/modules/java.desktop/javax/swing/text/html/parser/html32.bdtd