diff --git a/plugins/platforms/drm/egl_gbm_backend.cpp b/plugins/platforms/drm/egl_gbm_backend.cpp
--- a/plugins/platforms/drm/egl_gbm_backend.cpp
+++ b/plugins/platforms/drm/egl_gbm_backend.cpp
@@ -194,7 +194,7 @@
 
     qreal scale = output.output->scale();
 
-    glViewport(-v.x() * scale, (v.height() - overall.height() - v.y()) * scale,
+    glViewport(-v.x() * scale, (v.height() - overall.height() + v.y()) * scale,
                overall.width() * scale, overall.height() * scale);
     return true;
 }
diff --git a/plugins/platforms/x11/windowed/egl_x11_backend.cpp b/plugins/platforms/x11/windowed/egl_x11_backend.cpp
--- a/plugins/platforms/x11/windowed/egl_x11_backend.cpp
+++ b/plugins/platforms/x11/windowed/egl_x11_backend.cpp
@@ -108,7 +108,7 @@
     // TODO: are the values correct?
 
     qreal scale = screens()->scale(screenId);
-    glViewport(-v.x(), v.height() - overall.height() - v.y(), overall.width() * scale, overall.height() * scale);
+    glViewport(-v.x(), v.height() - overall.height() + v.y(), overall.width() * scale, overall.height() * scale);
 }
 
 void EglX11Backend::endRenderingFrameForScreen(int screenId, const QRegion &renderedRegion, const QRegion &damagedRegion)