diff --git a/lib/optimizer/tests/SpecTest.php b/lib/optimizer/tests/SpecTest.php
index 8d417ea6078..a48c4f78fc1 100644
--- a/lib/optimizer/tests/SpecTest.php
+++ b/lib/optimizer/tests/SpecTest.php
@@ -30,6 +30,8 @@ final class SpecTest extends TestCase
         'ReorderHead - reorders_head_a4a'                => 'see https://github.com/ampproject/amp-toolbox/issues/583',
         'ReorderHead - reorders_head_amphtml'            => 'see https://github.com/ampproject/amp-toolbox/issues/583',
         'ReorderHead - preserves_amp_custom_style_order' => 'see https://github.com/ampproject/amp-toolbox/issues/604',
+
+        'ServerSideRendering - converts_sizes_attribute_to_css' => 'see https://github.com/ampproject/amp-toolbox/issues/819',
     ];
 
     const CLASS_SKIP_TEST = '__SKIP__';