diff --git a/Source/WebKit2/WebProcess/WebPage/qt/LayerTreeHostQt.cpp b/Source/WebKit2/WebProcess/WebPage/qt/LayerTreeHostQt.cpp
index c296481..e93a28f 100644
--- a/Source/WebKit2/WebProcess/WebPage/qt/LayerTreeHostQt.cpp
+++ b/Source/WebKit2/WebProcess/WebPage/qt/LayerTreeHostQt.cpp
@@ -554,6 +554,7 @@ void LayerTreeHostQt::purgeBackingStores()

 UpdateAtlas& LayerTreeHostQt::getAtlas(ShareableBitmap::Flags flags)
 {
+    m_updateAtlases.clear();
     for (int i = 0; i < m_updateAtlases.size(); ++i) {
         if (m_updateAtlases[i].flags() == flags)
             return m_updateAtlases[i];