diff -up ./build.xml.tests-headless ./build.xml
--- ./build.xml.tests-headless	2012-03-07 11:56:41.702657823 +0100
+++ ./build.xml	2012-03-07 11:57:12.635887659 +0100
@@ -561,6 +561,7 @@
       <sysproperty key="jna.protected" value="true"/>
       <sysproperty key="jna.builddir" file="${build}"/>
       <jvmarg value="${vmopt.arch}"/>
+      <jvmarg value="-Djava.awt.headless=true"/>
       <classpath><path refid="test.runpath"/></classpath>
       <formatter type="brief" usefile="false"/>
       <formatter type="xml"/>