diff --git a/src/corelib/thread/qthread_win.cpp b/src/corelib/thread/qthread_win.cpp
index bab6cf85de..bdade1d24e 100644
--- a/src/corelib/thread/qthread_win.cpp
+++ b/src/corelib/thread/qthread_win.cpp
@@ -300,7 +300,7 @@ void QThreadPrivate::createEventDispatcher(QThreadData *data)
 
 #ifndef QT_NO_THREAD
 
-unsigned int __stdcall QThreadPrivate::start(void *arg)
+unsigned int __stdcall QT_ENSURE_STACK_ALIGNED_FOR_SSE QThreadPrivate::start(void *arg)
 {
     QThread *thr = reinterpret_cast<QThread *>(arg);
     QThreadData *data = QThreadData::get2(thr);