diff --git a/src/config.h.in b/src/config.h.in
index 9f50fa3f47360071430e63985315006b5aaeb248..07ca44cfbd73e04cf7917909fd3e55b1f15c8b22 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -89,3 +89,5 @@
 /* Define if you have the <limits.h> header file */
 #undef HAVE_LIMITS_H
 
+/* type to use in place of socklen_t if not defined */
+#undef socklen_t