=== modified file 'pmt/src/lib/pmt.cc'
--- pmt/src/lib/pmt.cc	2008-06-26 17:17:15 +0000
+++ pmt/src/lib/pmt.cc	2009-01-30 14:36:53 +0000
@@ -864,7 +864,7 @@
 pmt_t
 pmt_nthcdr(size_t n, pmt_t list)
 {
-  if (!(pmt_is_null(list) || pmt_is_pair(list)))
+  if (!(pmt_is_pair(list) || pmt_is_null(list)))
     throw pmt_wrong_type("pmt_nthcdr", list);
     
   while (n > 0){