diff --git a/mrbgems/mruby-time/src/time.c b/mrbgems/mruby-time/src/time.c
index 50d618fc3..626fcdcd0 100644
--- a/mrbgems/mruby-time/src/time.c
+++ b/mrbgems/mruby-time/src/time.c
@@ -21,7 +21,9 @@
 #endif
 
 #include <stdlib.h>
+#ifdef _WIN32
 #include <unistd.h>
+#endif
 
 #define NDIV(x,y) (-(-((x)+1)/(y))-1)
 #define TO_S_FMT "%Y-%m-%d %H:%M:%S "