diff --git a/build.xml b/build.xml
index b1ff647..6cf025f 100644
--- a/build.xml
+++ b/build.xml
@@ -47,24 +47,28 @@
 <target name="compose-tiles" depends="init-builddir,compile">
 <java classname="micropolisj.build_tool.MakeTiles" classpath="${builddir}"
 	fork="true" failonerror="true" dir="graphics" inputstring="">
+	<sysproperty key="java.awt.headless" value="true" />
 	<arg file="graphics/tiles.rc" />
 	<arg file="${builddir}/16x16" />
 	<assertions><enable/></assertions>
 </java>
 <java classname="micropolisj.build_tool.MakeTiles" classpath="${builddir}"
 	fork="true" failonerror="true" dir="graphics" inputstring="">
+	<sysproperty key="java.awt.headless" value="true" />
 	<sysproperty key="tile_size" value="8" />
 	<arg file="graphics/tiles.rc" />
 	<arg file="${builddir}/8x8" />
 </java>
 <java classname="micropolisj.build_tool.MakeTiles" classpath="${builddir}"
 	fork="true" failonerror="true" dir="graphics" inputstring="">
+	<sysproperty key="java.awt.headless" value="true" />
 	<sysproperty key="tile_size" value="32" />
 	<arg file="graphics/tiles.rc" />
 	<arg file="${builddir}/32x32" />
 </java>
 <java classname="micropolisj.build_tool.MakeTiles" classpath="${builddir}"
 	fork="true" failonerror="true" dir="graphics" inputstring="">
+	<sysproperty key="java.awt.headless" value="true" />
 	<sysproperty key="tile_size" value="3" />
 	<arg file="graphics/tiles.rc" />
 	<arg file="${builddir}/sm" />