Fix unix/posix.h include guard
diff --git a/src/unix/posix.h b/src/unix/posix.h
index 1e41bcf..ccdc753 100644
--- a/src/unix/posix.h
+++ b/src/unix/posix.h
@@ -4,8 +4,8 @@
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
-#ifndef INCLUDE_posix__w32_h__
-#define INCLUDE_posix__w32_h__
+#ifndef INCLUDE_posix__unix_h__
+#define INCLUDE_posix__unix_h__
#include <stdio.h>
#include <sys/param.h>