diff -r 896eb8056e97 -r d87a8838afa4 src/Pure/General/file.ML
--- a/src/Pure/General/file.ML	Wed Apr 26 20:34:11 2006 +0200
+++ b/src/Pure/General/file.ML	Wed Apr 26 22:38:05 2006 +0200
@@ -103,7 +103,7 @@
 fun mkdir path = system_command ("mkdir -p " ^ shell_path path);
 
 fun is_dir path =
-  if_none (try OS.FileSys.isDir (platform_path path)) false;
+  the_default false (try OS.FileSys.isDir (platform_path path));
 
 
 (* read / write files *)