diff --git a/runners/windows/windowsrunner.h b/runners/windows/windowsrunner.h
index 016b7c40f..a106af8b0 100644
--- a/runners/windows/windowsrunner.h
+++ b/runners/windows/windowsrunner.h
@@ -1,67 +1,69 @@
 /***************************************************************************
  *   Copyright 2009 by Martin Gräßlin <kde@martin-graesslin.com>           *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU General Public License as published by  *
  *   the Free Software Foundation; either version 2 of the License, or     *
  *   (at your option) any later version.                                   *
  *                                                                         *
  *   This program is distributed in the hope that it will be useful,       *
  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  *   GNU General Public License for more details.                          *
  *                                                                         *
  *   You should have received a copy of the GNU General Public License     *
  *   along with this program; if not, write to the                         *
  *   Free Software Foundation, Inc.,                                       *
  *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA .        *
  ***************************************************************************/
 #ifndef WINDOWSRUNNER_H
 #define WINDOWSRUNNER_H
 
 #include <KRunner/AbstractRunner>
 
+#include <QMutex>
+
 class KWindowInfo;
 
 class WindowsRunner : public Plasma::AbstractRunner
 {
     Q_OBJECT
 
     public:
         WindowsRunner(QObject* parent, const QVariantList &args);
         ~WindowsRunner() override;
 
         void match(Plasma::RunnerContext& context) override;
         void run(const Plasma::RunnerContext& context, const Plasma::QueryMatch& match) override;
 
     private Q_SLOTS:
         void prepareForMatchSession();
         void matchSessionComplete();
         void gatherInfo();
 
     private:
         enum WindowAction {
             ActivateAction,
             CloseAction,
             MinimizeAction,
             MaximizeAction,
             FullscreenAction,
             ShadeAction,
             KeepAboveAction,
             KeepBelowAction
         };
         Plasma::QueryMatch desktopMatch(int desktop, qreal relevance = 1.0);
         Plasma::QueryMatch windowMatch(const KWindowInfo& info, WindowAction action, qreal relevance = 1.0,
                                        Plasma::QueryMatch::Type type = Plasma::QueryMatch::ExactMatch);
         bool actionSupported(const KWindowInfo& info, WindowAction action);
 
         QHash<WId, KWindowInfo> m_windows; // protected by m_mutex
         QHash<WId, QIcon> m_icons; // protected by m_mutex
         QStringList m_desktopNames; // protected by m_mutex
         QMutex m_mutex;
 
         bool m_inSession : 1; // only used in the main thread
         bool m_ready : 1; // protected by m_mutex
 };
 
 #endif // WINDOWSRUNNER_H