diff --git a/MSVC/unistd.h b/MSVC/unistd.h
index a94ab7ca699801aca0fc8ff2a9a2d22dce06d8aa..7b626739752026ef5cd7db02d80e899c32e68c9a 100644
--- a/MSVC/unistd.h
+++ b/MSVC/unistd.h
@@ -26,6 +26,7 @@
 #include <process.h>
 #include <direct.h>
 #include <fcntl.h>
+#include <io.h>
 
 #define R_OK    4
 #define W_OK    2