diff --git a/acconfig.h b/acconfig.h
index e3366488..192dc0f8 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -12,3 +12,6 @@
 
 /* Define this if you have the `union wait' type in <sys/wait.h>.  */
 #undef HAVE_UNION_WAIT
+
+/* Define this if the POSIX.1 call `sysconf (_SC_OPEN_MAX)' works properly.  */
+#undef HAVE_SYSCONF_OPEN_MAX