diff --git a/src/global.c b/src/global.c
index 15baf1eb8..2ed5b4c6d 100644
--- a/src/global.c
+++ b/src/global.c
@@ -74,7 +74,7 @@ static void git__shutdown(void)
 #if defined(GIT_THREADS) && defined(GIT_WIN32)
 
 static DWORD _tls_index;
-static DWORD _mutex = 0;
+static volatile LONG _mutex = 0;
 
 static int synchronized_threads_init()
 {