--- a/scbayes.in
+++ b/scbayes.in
@@ -16,6 +16,7 @@
 
 (use gauche.parseopt)
 (use gauche.parameter)
+(use gauche.version)
 (use dbm)
 (use dbm.gdbm) ;; should be customizable
 (use util.digest)
@@ -130,12 +131,18 @@
      (sys-rename (temporary-table-file) (table-file))
      (sys-rename (temporary-digest-file) (digest-file)))))
 
-(define (lock)
-  (unless (eq? (create-directory* (lock-file)) #t)
-     (scmail-wformat "~a is now being updated" (table-file))
-     (scmail-wformat "or perhaps ~a is staled." (lock-file))
-     (scmail-eformat "(Please remove the lock file if it is staled.)"))
-  )
+(if (version<? (gauche-version) "0.9")
+    (define (lock)
+      (unless (eq? (create-directory* (lock-file)) #t)
+        (scmail-wformat "~a is now being updated" (table-file))
+        (scmail-wformat "or perhaps ~a is staled." (lock-file))
+        (scmail-eformat "(Please remove the lock file if it is staled.)")))
+    (define (lock)
+      (guard (e (else
+                 (scmail-wformat "~a is now being updated" (table-file))
+                 (scmail-wformat "or perhaps ~a is staled." (lock-file))
+                 (scmail-eformat "(Please remove the lock file if it is staled.)")))
+        (create-directory* (lock-file)))))
 
 (define force-learn? (make-parameter #f))