diff --git a/libguile/weaks.h b/libguile/weaks.h
index 908e27628..23b707248 100644
--- a/libguile/weaks.h
+++ b/libguile/weaks.h
@@ -3,7 +3,7 @@
 #ifndef SCM_WEAKS_H
 #define SCM_WEAKS_H
 
-/* Copyright (C) 1995,1996,2000,2001, 2003, 2006, 2008 Free Software Foundation, Inc.
+/* Copyright (C) 1995,1996,2000,2001, 2003, 2006, 2008, 2009 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -71,10 +71,12 @@ SCM_API SCM scm_doubly_weak_pair (SCM car, SCM cdr);
   ((SCM_WEAK_PAIR_CAR_DELETED_P (_cell))	\
    || (SCM_WEAK_PAIR_CDR_DELETED_P (_cell)))
 
-/* Accessing the components of a weak cell.  */
+/* Accessing the components of a weak cell.  These return `SCM_UNDEFINED' if
+   the car/cdr has been collected.  */
 #define SCM_WEAK_PAIR_WORD(_cell, _word)		\
-  ((SCM_WEAK_PAIR_WORD_DELETED_P ((_cell), (_word)))	\
-   ? SCM_BOOL_F : SCM_CAR (pair))
+  (SCM_WEAK_PAIR_WORD_DELETED_P ((_cell), (_word))	\
+   ? SCM_UNDEFINED					\
+   : SCM_CELL_OBJECT ((_cell), (_word)))
 #define SCM_WEAK_PAIR_CAR(_cell)  (SCM_WEAK_PAIR_WORD ((_cell), 0))
 #define SCM_WEAK_PAIR_CDR(_cell)  (SCM_WEAK_PAIR_WORD ((_cell), 1))