diff --git a/arguments.c b/arguments.c
index ca828f00..e699834c 100644
--- a/arguments.c
+++ b/arguments.c
@@ -20,6 +20,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "tmux.h"