diff -r 9efdebe24c65 -r 0ffcad1f6130 src/Pure/General/path.scala
--- a/src/Pure/General/path.scala	Mon Mar 01 20:12:09 2021 +0100
+++ b/src/Pure/General/path.scala	Mon Mar 01 22:22:12 2021 +0100
@@ -143,7 +143,7 @@
 
   /* case-insensitive names */
 
-  def check_case_insensitive(paths: List[Path])
+  def check_case_insensitive(paths: List[Path]): Unit =
   {
     val table =
       (Multi_Map.empty[String, String] /: paths)({ case (tab, path) =>