diff --git a/mrbgems/mruby-time/src/time.c b/mrbgems/mruby-time/src/time.c
index 626fcdcd0..63d2f1c5b 100644
--- a/mrbgems/mruby-time/src/time.c
+++ b/mrbgems/mruby-time/src/time.c
@@ -21,7 +21,7 @@
 #endif
 
 #include <stdlib.h>
-#ifdef _WIN32
+#ifndef _WIN32
 #include <unistd.h>
 #endif