--- a/widget/headless/HeadlessWidget.cpp
+++ b/widget/headless/HeadlessWidget.cpp
@@ -282,17 +282,17 @@ HeadlessWidget::Move(double aX, double a
   mBounds.x = x;
   mBounds.y = y;
   NotifyRollupGeometryChange();
 }
 
 LayoutDeviceIntPoint
 HeadlessWidget::WidgetToScreenOffset()
 {
-  return LayoutDeviceIntPoint(mBounds.x, mBounds.y);
+  return mTopLevel->GetBounds().TopLeft();
 }
 
 LayerManager*
 HeadlessWidget::GetLayerManager(PLayerTransactionChild* aShadowManager,
                                 LayersBackend aBackendHint,
                                 LayerManagerPersistence aPersistence)
 {
   return nsBaseWidget::GetLayerManager(aShadowManager, aBackendHint, aPersistence);