diff -r 9efdebe24c65 -r 0ffcad1f6130 src/Pure/Tools/check_keywords.scala
--- a/src/Pure/Tools/check_keywords.scala	Mon Mar 01 20:12:09 2021 +0100
+++ b/src/Pure/Tools/check_keywords.scala	Mon Mar 01 22:22:12 2021 +0100
@@ -35,7 +35,7 @@
     progress: Progress,
     keywords: Keyword.Keywords,
     check: Set[String],
-    paths: List[Path])
+    paths: List[Path]): Unit =
   {
     val parallel_args = paths.map(path => (File.read(path), Token.Pos.file(path.expand.implode)))