diff --git a/src/autoconf.h.in b/src/autoconf.h.in
index 4aa0665..99cfcef 100644
--- a/src/autoconf.h.in
+++ b/src/autoconf.h.in
@@ -36,6 +36,9 @@
 /* Define to 1 if you have the <string.h> header file. */
 #undef HAVE_STRING_H
 
+/* Define to 1 if you have the <sys/mman.h> header file. */
+#undef HAVE_SYS_MMAN_H
+
 /* Define to 1 if you have the <sys/stat.h> header file. */
 #undef HAVE_SYS_STAT_H