diff --git a/mrbgems/mruby-socket/test/sockettest.c b/mrbgems/mruby-socket/test/sockettest.c
index cad5cac6c..234be38a0 100644
--- a/mrbgems/mruby-socket/test/sockettest.c
+++ b/mrbgems/mruby-socket/test/sockettest.c
@@ -23,6 +23,10 @@ mkstemp(char *p)
     return fd;
   return -1;
 }
+#else
+
+#include <io.h>
+
 #endif
 
 #else