--- Gauche-qdbm-0.2.orig/qdbm.scm
+++ Gauche-qdbm-0.2/qdbm.scm
@@ -72,7 +72,7 @@
   (unless (slot-bound? self 'path)
     (error "path must be set to open qdbm database"))
   (when (qdbm-file-of self)
-    (errorf "qdbm ~S already opened" qdbm))
+    (errorf "qdbm ~s already opened" (qdbm-file-of self)))
   (let* ((path   (slot-ref self 'path))
          (rwmode (slot-ref self 'rw-mode))
          (omode  (case rwmode