--- a/etc/settings Mon Feb 23 14:50:30 2015 +0100
+++ b/etc/settings Mon Feb 23 15:04:12 2015 +0100
@@ -34,7 +34,7 @@
###
ISABELLE_BUILD_OPTIONS=""
-ISABELLE_BUILD_JAVA_OPTIONS="-Xmx1024m -Xss1m"
+ISABELLE_BUILD_JAVA_OPTIONS="-Djava.awt.headless=true -Xmx1024m -Xss1m"
###