diff --git a/config.h.in b/config.h.in
index da75401..7a7587a 100644
--- a/config.h.in
+++ b/config.h.in
@@ -99,6 +99,9 @@
 /* Define if you have the <sys/dir.h> header file.  */
 #undef HAVE_SYS_DIR_H
 
+/* Define if you have the <sys/mman.h> header file.  */
+#undef HAVE_SYS_MMAN_H
+
 /* Define if you have the <sys/ndir.h> header file.  */
 #undef HAVE_SYS_NDIR_H