diff -r fd487d261169 -r 5036edb025b7 src/Pure/PIDE/session.scala
--- a/src/Pure/PIDE/session.scala	Sat Apr 04 18:05:37 2020 +0200
+++ b/src/Pure/PIDE/session.scala	Sat Apr 04 18:13:05 2020 +0200
@@ -687,7 +687,7 @@
   {
     val snapshot = this.snapshot()
     if (snapshot.is_outdated) {
-      Thread.sleep(output_delay.ms)
+      output_delay.sleep
       await_stable_snapshot()
     }
     else snapshot