diff -r b91dc7ab3464 -r df5dc24ca712 lib/Tools/build
--- a/lib/Tools/build	Wed Jan 28 22:19:22 2015 +0100
+++ b/lib/Tools/build	Wed Jan 28 22:50:00 2015 +0100
@@ -137,7 +137,7 @@
   echo
 fi
 
-declare -a JAVA_ARGS; eval "JAVA_ARGS=($ISABELLE_BUILD_JAVA_OPTIONS)"
+declare -a JAVA_ARGS; eval "JAVA_ARGS=(-Djava.awt.headless=true $ISABELLE_BUILD_JAVA_OPTIONS)"
 
 . "$ISABELLE_HOME/lib/scripts/timestart.bash"