diff --git a/src/corelib/thread/qmutex.h b/src/corelib/thread/qmutex.h
index be62dc01d6..e185041b13 100644
--- a/src/corelib/thread/qmutex.h
+++ b/src/corelib/thread/qmutex.h
@@ -12,11 +12,8 @@
 #include <chrono>
 #include <limits>
 
-class tst_QMutex;
-
 QT_BEGIN_NAMESPACE
 
-
 #if QT_CONFIG(thread) || defined(Q_QDOC)
 
 #if defined(Q_OS_LINUX) || defined(Q_OS_WIN) // these platforms use futex