diff --git a/src/plugins/platforms/wayland/qwaylandshm_p.h b/src/plugins/platforms/wayland/qwaylandshm_p.h
index 2f06b8b9d47..80d2b94923c 100644
--- a/src/plugins/platforms/wayland/qwaylandshm_p.h
+++ b/src/plugins/platforms/wayland/qwaylandshm_p.h
@@ -40,6 +40,17 @@
 #ifndef QWAYLANDSHM_H
 #define QWAYLANDSHM_H
 
+//
+//  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.
+//
+
 #include <QVector>
 #include <QImage>