--- a/gfx/layers/UpdateImageHelper.h
+++ b/gfx/layers/UpdateImageHelper.h
@@ -14,23 +14,26 @@
 #include "mozilla/gfx/Types.h"
 
 namespace mozilla {
 namespace layers {
 
 class UpdateImageHelper
 {
 public:
-  UpdateImageHelper(ImageContainer* aImageContainer, ImageClient* aImageClient, gfx::IntSize aImageSize) :
+  UpdateImageHelper(ImageContainer* aImageContainer,
+                    ImageClient* aImageClient,
+                    gfx::IntSize aImageSize,
+                    gfx::SurfaceFormat aFormat) :
     mImageContainer(aImageContainer),
     mImageClient(aImageClient),
     mImageSize(aImageSize),
     mIsLocked(false)
   {
-    mTexture = mImageClient->GetTextureClientRecycler()->CreateOrRecycle(gfx::SurfaceFormat::B8G8R8A8,
+    mTexture = mImageClient->GetTextureClientRecycler()->CreateOrRecycle(aFormat,
                                                                          mImageSize,
                                                                          BackendSelector::Content,
                                                                          TextureFlags::DEFAULT);
     if (!mTexture) {
       return;
     }
 
     mIsLocked = mTexture->Lock(OpenMode::OPEN_WRITE_ONLY);

--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -443,36 +443,39 @@ WebRenderLayerManager::GenerateFallbackD
 
       if (!lastBounds.IsEqualInterior(clippedBounds)) {
         invalidRegion.OrWith(lastBounds);
         invalidRegion.OrWith(clippedBounds);
       }
     }
   }
 
+  gfx::SurfaceFormat format = aItem->GetType() == nsDisplayItem::TYPE_MASK ?
+                                                    gfx::SurfaceFormat::A8 : gfx::SurfaceFormat::B8G8R8A8;
   if (!geometry || !invalidRegion.IsEmpty() || fallbackData->IsInvalid()) {
     if (gfxPrefs::WebRenderBlobImages()) {
       RefPtr<gfx::DrawEventRecorderMemory> recorder = MakeAndAddRef<gfx::DrawEventRecorderMemory>();
+      // TODO: should use 'format' to replace gfx::SurfaceFormat::B8G8R8X8. Currently blob image doesn't support A8 format.
       RefPtr<gfx::DrawTarget> dummyDt =
         gfx::Factory::CreateDrawTarget(gfx::BackendType::SKIA, gfx::IntSize(1, 1), gfx::SurfaceFormat::B8G8R8X8);
       RefPtr<gfx::DrawTarget> dt = gfx::Factory::CreateRecordingDrawTarget(recorder, dummyDt, imageSize.ToUnknownSize());
       PaintItemByDrawTarget(aItem, dt, aImageRect, aOffset, aDisplayListBuilder);
       recorder->Finish();
 
       wr::ByteBuffer bytes(recorder->mOutputStream.mLength, (uint8_t*)recorder->mOutputStream.mData);
       wr::ImageKey key = WrBridge()->GetNextImageKey();
       WrBridge()->SendAddBlobImage(key, imageSize.ToUnknownSize(), imageSize.width * 4, dt->GetFormat(), bytes);
       fallbackData->SetKey(key);
     } else {
       fallbackData->CreateImageClientIfNeeded();
       RefPtr<ImageClient> imageClient = fallbackData->GetImageClient();
       RefPtr<ImageContainer> imageContainer = LayerManager::CreateImageContainer();
 
       {
-        UpdateImageHelper helper(imageContainer, imageClient, imageSize.ToUnknownSize());
+        UpdateImageHelper helper(imageContainer, imageClient, imageSize.ToUnknownSize(), format);
         {
           RefPtr<gfx::DrawTarget> dt = helper.GetDrawTarget();
           PaintItemByDrawTarget(aItem, dt, aImageRect, aOffset, aDisplayListBuilder);
         }
         if (!helper.UpdateImage()) {
           return nullptr;
         }
       }

--- a/gfx/layers/wr/WebRenderPaintedLayer.cpp
+++ b/gfx/layers/wr/WebRenderPaintedLayer.cpp
@@ -52,17 +52,17 @@ WebRenderPaintedLayer::SetupExternalImag
 bool
 WebRenderPaintedLayer::UpdateImageClient()
 {
   MOZ_ASSERT(WrManager()->GetPaintedLayerCallback());
   nsIntRegion visibleRegion = GetVisibleRegion().ToUnknownRegion();
   IntRect bounds = visibleRegion.GetBounds();
   IntSize imageSize = bounds.Size();
 
-  UpdateImageHelper helper(mImageContainer, mImageClient, imageSize);
+  UpdateImageHelper helper(mImageContainer, mImageClient, imageSize, gfx::SurfaceFormat::B8G8R8A8);
 
   {
     RefPtr<DrawTarget> target = helper.GetDrawTarget();
     if (!target) {
       return false;
     }
 
     target->ClearRect(Rect(0, 0, imageSize.width, imageSize.height));