diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index e06951071f..afbde03619 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -568,12 +568,11 @@ QRectF QWindowPrivate::closestAcceptableGeometry(const QRectF &rect) const
 }
 
 void QWindowPrivate::setMinOrMaxSize(QSize *oldSizeMember, const QSize &size,
-                                     std::function<void()> funcWidthChanged,
-                                     std::function<void()> funcHeightChanged)
+                                     qxp::function_ref<void()> funcWidthChanged,
+                                     qxp::function_ref<void()> funcHeightChanged)
 {
     Q_Q(QWindow);
     Q_ASSERT(oldSizeMember);
-    Q_ASSERT(funcWidthChanged && funcHeightChanged);
     const QSize adjustedSize =
             size.expandedTo(QSize(0, 0)).boundedTo(QSize(QWINDOWSIZE_MAX, QWINDOWSIZE_MAX));
     if (*oldSizeMember == adjustedSize)
diff --git a/src/gui/kernel/qwindow_p.h b/src/gui/kernel/qwindow_p.h
index 3212a1d6fa..cf6a6934eb 100644
--- a/src/gui/kernel/qwindow_p.h
+++ b/src/gui/kernel/qwindow_p.h
@@ -22,6 +22,7 @@
 
 #include <QtCore/private/qobject_p.h>
 #include <QtCore/qelapsedtimer.h>
+#include <QtCore/qxpfunctional.h>
 #include <QtGui/QIcon>
 
 QT_BEGIN_NAMESPACE
@@ -74,8 +75,8 @@ public:
     virtual QRectF closestAcceptableGeometry(const QRectF &rect) const;
 
     void setMinOrMaxSize(QSize *oldSizeMember, const QSize &size,
-                         std::function<void()> funcWidthChanged,
-                         std::function<void()> funcHeightChanged);
+                         qxp::function_ref<void()> funcWidthChanged,
+                         qxp::function_ref<void()> funcHeightChanged);
 
     virtual void processSafeAreaMarginsChanged() {}