diff --git a/libs/ui/KisInMemoryFrameCacheSwapper.cpp b/libs/ui/KisInMemoryFrameCacheSwapper.cpp
index 299ebdfa49..f5ecaab208 100644
--- a/libs/ui/KisInMemoryFrameCacheSwapper.cpp
+++ b/libs/ui/KisInMemoryFrameCacheSwapper.cpp
@@ -1,82 +1,84 @@
 /*
  *  Copyright (c) 2018 Dmitry Kazakov <dimula73@gmail.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.
  */
 #include "KisInMemoryFrameCacheSwapper.h"
 
 #include <QMap>
 #include <kis_update_info.h>
 
 
 struct KRITAUI_NO_EXPORT KisInMemoryFrameCacheSwapper::Private
 {
     QMap<int, KisOpenGLUpdateInfoSP> framesMap;
 };
 
 KisInMemoryFrameCacheSwapper::KisInMemoryFrameCacheSwapper()
     : m_d(new Private)
 {
 }
 
 KisInMemoryFrameCacheSwapper::~KisInMemoryFrameCacheSwapper()
 {
 }
 
 void KisInMemoryFrameCacheSwapper::saveFrame(int frameId, KisOpenGLUpdateInfoSP info, const QRect &imageBounds)
 {
     Q_UNUSED(imageBounds);
     KIS_SAFE_ASSERT_RECOVER_NOOP(!m_d->framesMap.contains(frameId));
 
     m_d->framesMap.insert(frameId, info);
 }
 
 KisOpenGLUpdateInfoSP KisInMemoryFrameCacheSwapper::loadFrame(int frameId)
 {
     KIS_SAFE_ASSERT_RECOVER_NOOP(m_d->framesMap.contains(frameId));
     return m_d->framesMap.value(frameId, KisOpenGLUpdateInfoSP());
 }
 
 void KisInMemoryFrameCacheSwapper::moveFrame(int srcFrameId, int dstFrameId)
 {
     KIS_SAFE_ASSERT_RECOVER_RETURN(m_d->framesMap.contains(srcFrameId));
     KIS_SAFE_ASSERT_RECOVER_NOOP(!m_d->framesMap.contains(dstFrameId));
 
     m_d->framesMap[dstFrameId] = m_d->framesMap[srcFrameId];
     m_d->framesMap.remove(srcFrameId);
 }
 
 void KisInMemoryFrameCacheSwapper::forgetFrame(int frameId)
 {
     KIS_SAFE_ASSERT_RECOVER_RETURN(m_d->framesMap.contains(frameId));
     m_d->framesMap.remove(frameId);
 }
 
 bool KisInMemoryFrameCacheSwapper::hasFrame(int frameId) const
 {
     return m_d->framesMap.contains(frameId);
 }
 
 int KisInMemoryFrameCacheSwapper::frameLevelOfDetail(int frameId) const
 {
     KIS_SAFE_ASSERT_RECOVER_RETURN_VALUE(m_d->framesMap.contains(frameId), 0);
+    KIS_SAFE_ASSERT_RECOVER_RETURN_VALUE(!m_d->framesMap[frameId].isNull(), 0);
     return m_d->framesMap[frameId]->levelOfDetail();
 }
 
 QRect KisInMemoryFrameCacheSwapper::frameDirtyRect(int frameId) const
 {
     KIS_SAFE_ASSERT_RECOVER_RETURN_VALUE(m_d->framesMap.contains(frameId), QRect());
+    KIS_SAFE_ASSERT_RECOVER_RETURN_VALUE(!m_d->framesMap[frameId].isNull(), QRect());
     return m_d->framesMap[frameId]->dirtyImageRect();
 }