diff --git a/io/iom_wait.c b/io/iom_wait.c
index 1362651..b6a1e7b 100644
--- a/io/iom_wait.c
+++ b/io/iom_wait.c
@@ -1,4 +1,5 @@
 #define _POSIX_C_SOURCE 200809L
+#define _XOPEN_SOURCE 600
 #include "io_internal.h"
 #ifdef HAVE_EPOLL
 #include <sys/epoll.h>