diff -r 325593146d19 -r 3c32d1ac1de9 src/Pure/System/isabelle_system.scala
--- a/src/Pure/System/isabelle_system.scala	Sun Dec 22 14:11:31 2024 +0100
+++ b/src/Pure/System/isabelle_system.scala	Sun Dec 22 14:13:21 2024 +0100
@@ -390,7 +390,7 @@
   /* JVM shutdown hook */
 
   def create_shutdown_hook(body: => Unit): Thread = {
-    val shutdown_hook = Isabelle_Thread.create(new Runnable { def run: Unit = body })
+    val shutdown_hook = Isabelle_Thread.create(new Runnable { def run(): Unit = body })
 
     try { Runtime.getRuntime.addShutdownHook(shutdown_hook) }
     catch { case _: IllegalStateException => }