diff --git a/mccontrol.c b/mccontrol.c
index 7e8f9a9a..46b2ebaa 100644
--- a/mccontrol.c
+++ b/mccontrol.c
@@ -13,6 +13,7 @@
 #include <tcl.h>
 #include <time.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include "stringdict.h"
 #include "mccontrol.h"
 /*========================= life and death ==================================*/