diff --git a/lib/curl_setup.h b/lib/curl_setup.h
index 8381324aa2..b73dd65c5f 100644
--- a/lib/curl_setup.h
+++ b/lib/curl_setup.h
@@ -646,8 +646,10 @@ typedef HANDLE curl_win_thread_handle_t;
 #define CURL_WIN_BEGINTHREAD CreateThread
 #else
 #define CURL_THREAD_RETURN_T unsigned int
+#ifdef _WIN32
 typedef uintptr_t curl_win_thread_handle_t;
 #define CURL_WIN_BEGINTHREAD _beginthreadex
+#endif /* _WIN32 */
 #endif
 
 /*