diff --git a/src/plugins/platforms/cocoa/qnsview.h b/src/plugins/platforms/cocoa/qnsview.h
index cdcc9719f6..4ef2a7133d 100644
--- a/src/plugins/platforms/cocoa/qnsview.h
+++ b/src/plugins/platforms/cocoa/qnsview.h
@@ -62,7 +62,6 @@ Q_FORWARD_DECLARE_OBJC_CLASS(QT_MANGLE_NAMESPACE(QNSViewMouseMoveHelper));
     QPoint m_backingStoreOffset;
     QRegion m_maskRegion;
     CGImageRef m_maskImage;
-    uchar *m_maskData;
     bool m_shouldInvalidateWindowShadow;
     QPointer<QCocoaWindow> m_platformWindow;
     NSTrackingArea *m_trackingArea;