--- a/layout/painting/FrameLayerBuilder.cpp
+++ b/layout/painting/FrameLayerBuilder.cpp
@@ -5449,20 +5449,21 @@ ChooseScaleAndSetTransform(FrameLayerBui
       !aContainerFrame->HasPerspective()) {
     // If the container's transform is animated off main thread, fix a suitable scale size
     // for animation
     if (aContainerItem &&
         aContainerItem->GetType() == DisplayItemType::TYPE_TRANSFORM &&
         EffectCompositor::HasAnimationsForCompositor(
           aContainerFrame, eCSSProperty_transform)) {
       nsSize displaySize = ComputeDesiredDisplaySizeForAnimation(aContainerFrame);
-      // compute scale using the animation on the container (ignoring
-      // its ancestors)
+      // compute scale using the animation on the container, taking ancestors in to account
+      nsSize scaledVisibleSize = nsSize(aVisibleRect.Width() * aIncomingScale.mXScale,
+                                        aVisibleRect.Height() * aIncomingScale.mYScale);
       scale = nsLayoutUtils::ComputeSuitableScaleForAnimation(
-                aContainerFrame, aVisibleRect.Size(),
+                aContainerFrame, scaledVisibleSize,
                 displaySize);
       // multiply by the scale inherited from ancestors--we use a uniform
       // scale factor to prevent blurring when the layer is rotated.
       float incomingScale = std::max(aIncomingScale.mXScale, aIncomingScale.mYScale);
       scale.width *= incomingScale;
       scale.height *= incomingScale;
     } else {
       // Scale factors are normalized to a power of 2 to reduce the number of resolution changes