diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index 073f7c107..0d7543578 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -18,7 +18,7 @@
 #if defined(_WIN32) || defined(_WIN64)
   #include <winsock.h>
   #include <io.h>
-  #include <BaseTsd.h>
+  #include <basetsd.h>
   #define open  _open
   #define close _close
   #define dup _dup