diff --git a/gfx/layers/composite/ContainerLayerComposite.cpp b/gfx/layers/composite/ContainerLayerComposite.cpp
index f025b1e113c..000355482b4 100644
--- a/gfx/layers/composite/ContainerLayerComposite.cpp
+++ b/gfx/layers/composite/ContainerLayerComposite.cpp
@@ -57,7 +57,7 @@ GetOpaqueRect(Layer* aLayer)
 {
   nsIntRect result;
   gfx::Matrix matrix;
-  bool is2D = aLayer->GetBaseTransform().Is2D(&matrix);
+  bool is2D = aLayer->AsLayerComposite()->GetShadowTransform().Is2D(&matrix);
 
   // Just bail if there's anything difficult to handle.
   if (!is2D || aLayer->GetMaskLayer() ||