diff --git a/src/config.in b/src/config.in
index 782a316cf34..0d2b9ecbef3 100644
--- a/src/config.in
+++ b/src/config.in
@@ -142,6 +142,7 @@ Boston, MA 02111-1307, USA.  */
 #undef HAVE_LIBXMU
 #undef HAVE_LIBNCURSES
 #undef HAVE_LIBINTL
+#undef HAVE_LIBXP
 
 /* movemail Kerberos support */
 /* libraries */