diff --git a/src/corelib/thread/qthread_win.cpp b/src/corelib/thread/qthread_win.cpp
index e56fe2c6ae..5c7642c26e 100644
--- a/src/corelib/thread/qthread_win.cpp
+++ b/src/corelib/thread/qthread_win.cpp
@@ -99,6 +99,8 @@ void qt_create_tls()
         return;
     static QBasicMutex mutex;
     QMutexLocker locker(&mutex);
+    if (qt_current_thread_data_tls_index != TLS_OUT_OF_INDEXES)
+        return;
     qt_current_thread_data_tls_index = TlsAlloc();
 }