--- a/gfx/layers/client/TiledContentClient.cpp
+++ b/gfx/layers/client/TiledContentClient.cpp
@@ -1282,16 +1282,17 @@ ClientTiledLayerBuffer::ValidateTile(Til
     nsIntRect(aTileOrigin.x, aTileOrigin.y,
               GetScaledTileSize().width, GetScaledTileSize().height);
   // Intersect this area with the portion that's invalid.
   tileRegion.SubOut(GetValidRegion());
   tileRegion.SubOut(aDirtyRegion); // Has now been validated
 
   backBuffer->SetWaste(tileRegion.Area() * mResolution * mResolution);
   backBuffer->Unlock();
+  backBuffer->SyncWithObject(mCompositableClient->GetForwarder()->GetSyncObject());
 
   if (createdTextureClient) {
     if (!mCompositableClient->AddTextureClient(backBuffer)) {
       NS_WARNING("Failed to add tile TextureClient.");
       aTile.DiscardFrontBuffer();
       aTile.DiscardBackBuffer();
       return aTile;
     }