diff --git a/buffer/buffer_putflush.c b/buffer/buffer_putflush.c
index 616b06d..a12f110 100644
--- a/buffer/buffer_putflush.c
+++ b/buffer/buffer_putflush.c
@@ -2,6 +2,7 @@
 #include <sys/types.h>
 #include <sys/uio.h>
 #include <errno.h>
+#include <unistd.h>
 #endif
 #include "buffer.h"