diff -r d83e7e444b43 -r 7202e12cb324 src/Pure/General/time.scala
--- a/src/Pure/General/time.scala	Sun May 16 13:14:16 2021 +0200
+++ b/src/Pure/General/time.scala	Sun May 16 13:34:27 2021 +0200
@@ -65,5 +65,5 @@
 
   def instant: Instant = Instant.ofEpochMilli(ms)
 
-  def sleep: Unit = Thread.sleep(ms)
+  def sleep(): Unit = Thread.sleep(ms)
 }