diff --git a/widget/windows/winrt/MetroWidget.h b/widget/windows/winrt/MetroWidget.h
index 68b84936e67..5e40d1cf4d6 100644
--- a/widget/windows/winrt/MetroWidget.h
+++ b/widget/windows/winrt/MetroWidget.h
@@ -123,6 +123,7 @@ public:
                                         LayersBackend aBackendHint = mozilla::layers::LAYERS_NONE,
                                         LayerManagerPersistence aPersistence = LAYER_MANAGER_CURRENT,
                                         bool* aAllowRetaining = nullptr);
+  virtual mozilla::layers::LayersBackend GetPreferredCompositorBackend() { return mozilla::layers::LAYERS_D3D11; }
 
   // IME related interfaces
   NS_IMETHOD_(void) SetInputContext(const InputContext& aContext,