diff --git a/src/platforms/xcb/kwindowsystem.cpp b/src/platforms/xcb/kwindowsystem.cpp
--- a/src/platforms/xcb/kwindowsystem.cpp
+++ b/src/platforms/xcb/kwindowsystem.cpp
@@ -60,7 +60,11 @@
         for (int i = 0; i < screenList.count(); ++i) {
             const QScreen *screen = screenList.at(i);
             connections << QObject::connect(screen, &QScreen::geometryChanged, dirtify);
-            region += screen->geometry();
+
+            QRect screenGeom = screen->geometry();
+            screenGeom.setHeight(screenGeom.height() * screen->devicePixelRatio());
+            screenGeom.setWidth(screenGeom.width() * screen->devicePixelRatio());
+            region += screenGeom;
         }
         displayGeometry = region.boundingRect();
         isDirty = false;