diff --git a/src/widgets/styles/qpixmapstyle_p.h b/src/widgets/styles/qpixmapstyle_p.h
index 84f806dfa5d..4f5d27c285c 100644
--- a/src/widgets/styles/qpixmapstyle_p.h
+++ b/src/widgets/styles/qpixmapstyle_p.h
@@ -39,6 +39,17 @@
 #include <QtWidgets/QCommonStyle>
 #include <QtWidgets/QTileRules>
 
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
 QT_BEGIN_NAMESPACE
 
 class QPixmapStylePrivate;