diff --git a/mrbgems/mruby-dir/test/dirtest.c b/mrbgems/mruby-dir/test/dirtest.c
index 3fbbdebcd..4f05080c6 100644
--- a/mrbgems/mruby-dir/test/dirtest.c
+++ b/mrbgems/mruby-dir/test/dirtest.c
@@ -13,6 +13,8 @@
 #if defined(_WIN32)
 #include <io.h>
 #include <direct.h>
+#else
+#include <unistd.h>
 #endif
 
 static void