diff -r 3d33847dc911 -r 982f0bf34804 lib/Tools/java
--- a/lib/Tools/java	Mon Jan 22 22:45:45 2018 +0100
+++ b/lib/Tools/java	Tue Jan 23 16:37:57 2018 +0100
@@ -10,4 +10,5 @@
 unset CLASSPATH
 
 isabelle_java java "${JAVA_ARGS[@]}" \
+  "-Djava.ext.dirs=$(platform_path "$ISABELLE_JDK_HOME/jre/lib/ext")" \
   -classpath "$(platform_path "$ISABELLE_CLASSPATH")" "$@"