Index: qtbase-opensource-src-5.5.1+dfsg/src/plugins/platforms/xcb/qxcbwindow.cpp
===================================================================
--- qtbase-opensource-src-5.5.1+dfsg.orig/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ qtbase-opensource-src-5.5.1+dfsg/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -174,7 +174,8 @@ static inline QRect mapLocalGeometryFrom
 
 QXcbScreen *QXcbWindow::parentScreen()
 {
-    return parent() ? static_cast<QXcbWindow*>(parent())->parentScreen() : m_xcbScreen;
+    return (parent() && parent()->window()->type() != Qt::ForeignWindow) ?
+        static_cast<QXcbWindow*>(parent())->parentScreen() : m_xcbScreen;
 }
 
 QPoint QXcbWindow::mapToNative(const QPoint &pos, const QXcbScreen *screen) const