--- a/jdk/make/Tools.gmk	Fri Mar 21 14:45:54 2014 +0100
+++ b/jdk/make/Tools.gmk	Mon Mar 24 10:40:19 2014 +0100
@@ -71,6 +71,7 @@
     build.tools.generatecharacter.CharacterName
 
 TOOL_DTDBUILDER = $(JAVA_SMALL) -Ddtd_home=$(JDK_TOPDIR)/make/data/dtdbuilder \
+    -Djava.awt.headless=true \
     -cp $(JDK_OUTPUTDIR)/btclasses build.tools.dtdbuilder.DTDBuilder
 
 TOOL_GENERATEBREAKITERATORDATA = $(JAVA_SMALL) \