--- a/lib/Tools/java	Wed Oct 19 16:01:07 2022 +0200
+++ b/lib/Tools/java	Thu Oct 20 14:59:39 2022 +0200
@@ -7,7 +7,7 @@
 eval "declare -a JAVA_ARGS=($ISABELLE_JAVA_SYSTEM_OPTIONS)"
 
 classpath "$ISABELLE_SETUP_CLASSPATH"; unset ISABELLE_SETUP_CLASSPATH
-classpath "$CLASSPATH"; unset CLASSPATH
+classpath "$CLASSPATH"; export CLASSPATH=""
 
 isabelle_java java "${JAVA_ARGS[@]}" \
   -classpath "$(platform_path "$ISABELLE_CLASSPATH")" "$@"