diff --git a/src/memgzio.h b/src/memgzio.h
index 2a6231e9..9489f993 100644
--- a/src/memgzio.h
+++ b/src/memgzio.h
@@ -9,7 +9,7 @@
  * Adapted from original gzio.c from zlib library by Forgotten
  */
 
-#if defined(HAVE_ZUTIL_H) || defined(_WIN32)
+#if defined(HAVE_ZUTIL_H) || defined(_MSC_VER)
 # include <zutil.h>
 #else
 #include <zlib.h>