diff --git a/after/syntax/css/css3-layout.vim b/after/syntax/css/css3-layout.vim
deleted file mode 100644
index 8742ead..0000000
--- a/after/syntax/css/css3-layout.vim
+++ /dev/null
@@ -1,3 +0,0 @@
-" TODO: create cssLayoutAttr group
-syn keyword cssFontAttr contained same
-syn keyword cssPseudoClassId contained slot
diff --git a/after/syntax/html.vim b/after/syntax/html.vim
index 09b7b3d..3928300 100644
--- a/after/syntax/html.vim
+++ b/after/syntax/html.vim
@@ -11,7 +11,6 @@ syn include @htmlCss syntax/css/css3-content.vim
 syn include @htmlCss syntax/css/css3-exclusions.vim
 syn include @htmlCss syntax/css/css3-fonts.vim
 syn include @htmlCss syntax/css/css3-images.vim
-syn include @htmlCss syntax/css/css3-layout.vim
 syn include @htmlCss syntax/css/css3-linebox.vim
 syn include @htmlCss syntax/css/css3-multicol.vim
 syn include @htmlCss syntax/css/css3-page.vim
diff --git a/test/test.css b/test/test.css
index ecd445c..2175512 100644
--- a/test/test.css
+++ b/test/test.css
@@ -269,10 +269,6 @@
   initial-letter-align: auto;
 }
 
-.layout::slot(b) {
-  display: same;
-}
-
 .line-grid {
   line-grid: create;
   line-snap: block-start;
diff --git a/test/test.html b/test/test.html
index 2a8304c..9e9f2cb 100644
--- a/test/test.html
+++ b/test/test.html
@@ -300,11 +300,6 @@
 }
 </style>
 <style>
-.layout::slot(b) {
-  display: same;
-}
-</style>
-<style>
 .line-grid {
   line-grid: create;
   line-snap: block-start;