diff -r a397fd0c451a -r 152d6c58adb3 src/Pure/Concurrent/consumer_thread.scala
--- a/src/Pure/Concurrent/consumer_thread.scala	Sat Jun 08 16:26:47 2024 +0200
+++ b/src/Pure/Concurrent/consumer_thread.scala	Sat Jun 08 19:35:28 2024 +0200
@@ -57,7 +57,7 @@
 
   private def failure(exn: Throwable): Unit =
     Output.error_message(
-      "Consumer thread failure: " + quote(thread.getName) + "\n" + Exn.message(exn))
+      "Consumer thread failure: " + quote(thread.getName) + "\n" + Exn.print(exn))
 
   private def robust_finish(): Unit =
     try { finish() } catch { case exn: Throwable => failure(exn) }