diff --git a/help.c b/help.c
index 399b0b40f4..9dae4e7551 100644
--- a/help.c
+++ b/help.c
@@ -126,7 +126,7 @@ static int is_executable(const char *name)
 	    !S_ISREG(st.st_mode))
 		return 0;
 
-#ifdef __MINGW32__
+#ifdef WIN32
 {	/* cannot trust the executable bit, peek into the file instead */
 	char buf[3] = { 0 };
 	int n;
diff --git a/run-command.c b/run-command.c
index d1df7abe9a..d0833f846e 100644
--- a/run-command.c
+++ b/run-command.c
@@ -67,7 +67,7 @@ int start_command(struct child_process *cmd)
 
 	trace_argv_printf(cmd->argv, "trace: run_command:");
 
-#ifndef __MINGW32__
+#ifndef WIN32
 	fflush(NULL);
 	cmd->pid = fork();
 	if (!cmd->pid) {
@@ -294,7 +294,7 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const
 	return run_command(&cmd);
 }
 
-#ifdef __MINGW32__
+#ifdef WIN32
 static __stdcall unsigned run_thread(void *data)
 {
 	struct async *async = data;
@@ -310,7 +310,7 @@ int start_async(struct async *async)
 		return error("cannot create pipe: %s", strerror(errno));
 	async->out = pipe_out[0];
 
-#ifndef __MINGW32__
+#ifndef WIN32
 	/* Flush stdio before fork() to avoid cloning buffers */
 	fflush(NULL);
 
@@ -339,7 +339,7 @@ int start_async(struct async *async)
 
 int finish_async(struct async *async)
 {
-#ifndef __MINGW32__
+#ifndef WIN32
 	int ret = 0;
 
 	if (wait_or_whine(async->pid))
diff --git a/run-command.h b/run-command.h
index e345502843..09a4cb25b2 100644
--- a/run-command.h
+++ b/run-command.h
@@ -79,7 +79,7 @@ struct async {
 	int (*proc)(int fd, void *data);
 	void *data;
 	int out;	/* caller reads from here and closes it */
-#ifndef __MINGW32__
+#ifndef WIN32
 	pid_t pid;
 #else
 	HANDLE tid;
diff --git a/setup.c b/setup.c
index e3781b656d..029371e584 100644
--- a/setup.c
+++ b/setup.c
@@ -41,7 +41,7 @@ const char *prefix_path(const char *prefix, int len, const char *path)
 const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
 {
 	static char path[PATH_MAX];
-#ifndef __MINGW32__
+#ifndef WIN32
 	if (!pfx || !*pfx || is_absolute_path(arg))
 		return arg;
 	memcpy(path, pfx, pfx_len);