diff --git a/libguile/boolean.h b/libguile/boolean.h
index 8f55f1ee5..df72728ef 100644
--- a/libguile/boolean.h
+++ b/libguile/boolean.h
@@ -3,7 +3,7 @@
 #ifndef SCM_BOOLEAN_H
 #define SCM_BOOLEAN_H
 
-/* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010 Free Software Foundation, Inc.
+/* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010, 2013 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
@@ -126,6 +126,7 @@ SCM_API int scm_to_bool (SCM x);
 
 SCM_API SCM scm_not (SCM x);
 SCM_API SCM scm_boolean_p (SCM obj);
+SCM_API SCM scm_nil_p (SCM obj);
 
 SCM_INTERNAL void scm_init_boolean (void);