diff --git a/src/core/bodypartformatterbasefactory_p.h b/src/core/bodypartformatterbasefactory_p.h
index 10a722b..1a06079 100644
--- a/src/core/bodypartformatterbasefactory_p.h
+++ b/src/core/bodypartformatterbasefactory_p.h
@@ -1,30 +1,30 @@
 // SPDX-FileCopyrightText: 2004 Marc Mutz <mutz@kde.org>
 // SPDX-FileCopyrightText: 2004 Ingo Kloecker <kloecker@kde.org>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
 
 #include "bodypartformatterbasefactory.h"
 #include <memory>
 #include <optional>
 
 namespace MimeTreeParser
 {
 class BodyPartFormatterBaseFactory;
 class ObjectTreeParser;
 
 class BodyPartFormatterBaseFactoryPrivate
 {
 public:
     BodyPartFormatterBaseFactoryPrivate(BodyPartFormatterBaseFactory *factory);
     ~BodyPartFormatterBaseFactoryPrivate();
 
     void setup();
     void messageviewer_create_builtin_bodypart_formatters(); // defined in bodypartformatter.cpp
     void insert(const char *type, const char *subtype, Interface::BodyPartFormatter *formatter);
 
-    BodyPartFormatterBaseFactory *q;
+    BodyPartFormatterBaseFactory *const q;
     std::optional<TypeRegistry> all;
 };
 
 }