diff --git a/src/config.h.in b/src/config.h.in
index 0d39b43..2b2730e 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -388,3 +388,6 @@
 
 /* Define if you want XSMP interaction as well as vanilla swapfile safety */
 #undef USE_XSMP_INTERACT
+
+/* Define if fcntl()'s F_SETFD command knows about FD_CLOEXEC */
+#undef HAVE_FD_CLOEXEC