diff -r 5036edb025b7 -r d5773922358d src/Pure/General/file_watcher.scala
--- a/src/Pure/General/file_watcher.scala	Sat Apr 04 18:13:05 2020 +0200
+++ b/src/Pure/General/file_watcher.scala	Sat Apr 04 19:18:19 2020 +0200
@@ -90,7 +90,7 @@
       handle(changed)
     }
 
-    private val watcher_thread = Standard_Thread.fork("File_Watcher", daemon = true)
+    private val watcher_thread = Standard_Thread.fork(name = "File_Watcher", daemon = true)
     {
       try {
         while (true) {