diff --git a/thirdparty/libz/gzguts.h b/thirdparty/libz/gzguts.h
index fb919855..2c1a1bb7 100644
--- a/thirdparty/libz/gzguts.h
+++ b/thirdparty/libz/gzguts.h
@@ -3,7 +3,9 @@
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
+#ifndef _WIN32
 #include <unistd.h>
+#endif
 
 #ifdef _LARGEFILE64_SOURCE
 #  ifndef _LARGEFILE_SOURCE